Post 1, March 13
Welcome To The Salmon Creek Tree Swallow Nest Box Project
Yes, welcome! Welcome to the Salmon Creek watershed of the Braddock Bay Wildlife Management Area of western New York, where with permission we’ve operated a Tree Swallow nest box project for many years and where we’ll take you with us as our birds experience one complete nesting season, from start to finish.
In case you’re not familiar with Tree Swallows here’s a couple important facts. They’re aerial insectivores, speedy little flying machines that catch most of their insect food while the birds themselves are in flight.
Tree Swallows are also cavity-nesters, but they have a major problem: they are unable to make the cavities they need to nest in. Luckily, they are highly adaptable birds and take eagerly to nest boxes we humans provide, and this is how we’ve helped at Salmon Creek. Years ago we carefully picked a spot we thought would be safe from both predators and most competing bird species, and that offered excellent feeding nearby. We put up a group of boxes which migrating Tree Swallows quickly found and used, and we’ve operated the project there ever since.
Each season these great little native songbirds more than repay our efforts by letting us into their lives, teaching us about the issues they confront and stimulating us to think of better ways to assist them. After every long winter we look forward eagerly to the return of the swallows and this year we’re glad you’ll be joining us as we follow our birds through their nesting cycle from start to finish. We guarantee you’ll learn a lot about birds in the process, so please come on along, we welcome the company! But before we begin our journey let’s check out the the project site itself.
Our Tree Swallow nest boxes are placed in a large, open field adjacent to sluggish, cattail-lined Salmon Creek, just a short swallow’s flight from more than 3000 acres of ponds, creeks, marshes, fields and woodlots along the south side of Lake Ontario. This is truly superior habitat for Tree Swallows. We’ve offered 8-12 boxes in a grid here each year for many years and never had an unused box. The boxes are spaced 120-150 feet apart in a grid located several hundred yards from buildings and positioned well away from mammalian predator travel lanes. Because of this placement we’ve had no nest predation to date and no problems with House Sparrows or House Wrens. Nesting success has been high, with failure of eggs to hatch or egg destruction during female takeovers causing most mortality. Except for one year, fledging rate of eggs that hatched was between 82-100%, and the project fledged over 400 young Tree Swallows over the previous nine seasons.
Each year we try to learn something new that will help us better understand and assist the swallows and that we can share with other Tree Swallow fans. This year we’re doing two things, this narrative being the first, but we also have another objective: we’re going to see if Tree Swallows will learn to accept mealworms from a specially-designed feeder. If they do it would help the adults survive periods of bad weather and ensure their nestlings a food supply through fledging. Some Purple Martins, the Tree Swallow’s big cousins, now accept supplemental feeding, so why not Tree Swallows? We’ll see!
Post 2, March 14
What A Strange, Strange Winter This Has Been!
Today, March 14, I put up the last of our 8 initial nest boxes and poles, the earliest I’ve been able to do this by two weeks! Normally the ground would still be frozen hard and probably snow-covered, but our region has had temperatures far above normal for weeks and virtually no snow to speak of since February! In the 23 years I’ve lived in this township this is by far the warmest and most snow-free winter I remember. And from what I’ve been reading these weather extremes have been widespread across eastern and central North America.
I was really hoping that for their sake I wouldn’t see Tree Swallows this morning, but I wasn’t surprised as I approached the nest box grid to hear the unmistakable shrill cries that signaled at least some had arrived, way ahead of schedule. My fear is that winter could still return in force, killing most of those Tree Swallows that have come north prematurely on the strong warm fronts that have swept across the continent in recent weeks. In the past we’ve had major swallow die-offs here well into April during cold spells, so these early-birds are in danger but don’t know it. However, the forecasts for the Rochester area call for 60-70 F degree weather for the next week, so the swallows should be ok for awhile at least. Are prey species of insects also responding to the warm conditions and becoming available for swallow food? I hope so.
It was interesting to see some Tree Swallows flying over the grid of boxes showing the stiff-winged “flutter flight” display. We’ve always been curious about this behavior, which some ornithologists theorize is a signal of sub-ordinance given by females prospecting for nest cavities. However, our early arrivals are probably males, not females, and unlike the authorities we believe the flutter flight doesn’t necessarily signal sub-ordinance, but rather tells other swallows “don’t mess with me.” In either case the flutter appears to be involved in establishing dominance relationships.
Post 3, March 15
It’s Cold Here Near The Big Lake!
Yesterday was beautiful here along the south shore of Lake Ontario, sunny and warm, but this morning is another story. It’s cloudy and a steady cold NE wind is blowing in from the lake. Lake Ontario is huge and deep, and takes months to really warm up each spring, so whenever the prevailing wind is out of the north the nearby land gets a cold blast. Even on sunny days with little wind the Tree Swallow Project field can be a chilly place. The sun warms the land, causing the air to rise, then cold air over the lake slides in underneath the rising warm air and nearshore areas can be 10-20 degrees F colder than locations just a few miles inland. All these micro-climatic factors affect how we manage our nest box project. For instance, box ventilation to prevent overheating is usually not the issue for us that it is in places subjected to sustained hot weather. Here we must take care that cold air doesn’t seep into the boxes, so we make them as air tight as possible, except for the entrance of course. The lesson is that you need to know your local conditions and how they affect whatever species you are managing for.
In spite of the cold wind there were 3 Tree Swallows at the project grid. They sailed back and forth at between 50-200 feet above ground, almost always facing into the wind, hanging in place at times. I think they must have been picking off wind-blown insects. I saw no insects flying at ground level today, although there were yesterday when it was warmer. At no time during the 45 minutes I was there did the swallows land on boxes. Finding food was clearly more important. I checked each of the 8 boxes for feces on the floors that would indicate overnight roosting inside, but there were none. I also checked a few sheltered spots along Salmon Creek for other swallows – none found.
As I left the field, I heard Eastern Bluebirds calling. There is usually a pair or two nesting in the general neighborhood each year, but they’ve never attempted to use our swallow boxes. They’d be welcome to, of course, but I suspect our grid is too far out in the open field for them, and offers no handy shrubs or trees for perching. This year I’m going to put up a box for bluebirds relatively near a hedgerow bordering the field, and if it is accepted, I’ll pair it with a swallow box so I can watch the two species interact.
Post 4, March 17
Yesterday, March 16, was absolutely gorgeous: warm SW winds kicked the temperature up to almost 70 F, pretty rare for March here in upstate NY, and not that common in April or May for that matter! But today’s a different story. We woke to find the neighborhood in a fog bank, formed as the wind, now from the NE, pushed moisture-laden air in from Lake Ontario.
I hadn’t been able to visit the boxes yesterday so today I was anxious to see what was going on. I waited for things to clear up, but by 10:00 AM boredom drove me to check the field. The fog was even denser there, and the breeze, though soft, was enough to chill. No swallows were present at the project, and I was unable to find any along Salmon Creek as I returned home.
A brief clear spell at 2:00 PM got me out again, but the fog rolled back in almost as soon as I reached the field. I brought the bluebird house and erected it within a short flight of bluebird perches in the hedgerow. This placement makes me a bit uneasy since there’s a chance House Sparrows might travel down the hedgerow from neighboring houses and barns and find it. If bluebirds haven’t taken this box within 2 weeks it’s coming down, and if House Sparrows show up during this time I’ll remove it regardless. I don’t want House Sparrows anywhere near the swallow grid, even if it means not having bluebirds.
Even though it was still foggy there Tree Swallows had returned to the project. I counted 6 dashing about the field calling excitedly, so a few more must have arrived yesterday, and unlike two days ago they were landing on the boxes. Based on behavior I believe there was at least one female among them. Since a string of very warm weather is forecast for the coming week – highs in the 70’s to 80!! – I expect swallow numbers will build up rapidly. We’ll see.
Post 5, March 18
The First Of Several Thousand Pictures
What a change from yesterday! Bright sunshine, no wind, mid-50 degrees by 10 AM, with temperatures supposed to hit the 70’s! Is this upstate NY or the Carolinas?
I visited the grid for an hour between 10-11 AM today, and there were from 1 to 7 Tree Swallows present at all times. I got the impression that birds were leaving temporarily to feed along Salmon Creek, and then returning, back and forth. There was considerable perching on boxes, darting from box to box, and chattering, as expected early in the season. At least two of the swallows, males, were acting very territorial at boxes 6 and 7 respectively. It’s impossible to tell if the swallows present today are experienced nesters from previous years returning to this grid or migrants passing through on their way to parts north or east, but I’ll bet the ones at boxes 6 and 7 at least were old friends from past years.
Another thing I wonder is where the swallows that nest in my boxes wintered. Since Tree Swallows passing the Braddock Bay Hawk Watch (roughly 1 mile away) almost always are seen moving from west to east, I’m inclined to think our population is birds that wintered in Louisiana or adjacent states, birds that came up the Mississippi/Ohio River Valleys west of the Appalachian Mountains, rather than birds that wintered in Florida.
This morning I took the first Tree Swallow photos of the season, the first of probably thousands I will shoot between now and mid-July. The swallows are not used to my presence yet and wouldn’t permit a close approach. That will change with time. Since I’ll be posting quite a few photos in the coming weeks I need to stress that I’m not a pro and I use a little Canon PowerShot handheld most of the time. I try my best but don’t expect perfection. Think what the pictures I don’t feel good enough to post must look like!
Also seen at the field this morning were a scattering of migrating raptors: Turkey Vultures, a Northern Harrier and a Cooper’s Hawk. The swallow project field is about 1 mile south of a major spring raptor flight path that passes over Braddock Bay. The Hawk Watcher there should count several hundred, perhaps even a thousand or more today if the weather holds. I usually know immediately when potential swallow predators such as Kestrels, Merlins, Cooper’s Hawks or Sharp-shinned Hawks migrate over the field; the swallows burst out with alarm calls and mount up into the sky, whirling about until the possible danger passes.
Post 6, March 21
The Good Weather Continues But No Increase In Swallows
I made very quick visits to the field 3/19 and 3/20, and a longer visit today, 3/21. While the weather here has continued to set warm temperature records – highs in the upper 70’s – the number of Tree Swallows present at our boxes has stayed a steady maximum of 7. While there’s no way I can verify it my gut feeling is that this little group all came in about one week ago and have remained. Some may be returns from previous years and some may be newcomers, but they seem to have either reached their goal or have paused here, attracted by the boxes set in superb habitat. I’m actually quite happy there hasn’t been a build-up of swallow numbers because this is still upstate NY, and there’s plenty of time yet for cold or even blizzards.
One reason I believe these have been the same birds all the last week is that the same boxes have been perched on day after day. Single birds, presumably males, appear to have claimed boxes 3, 5, 6, and 7. Each bird has been seen perching on its box, surveying the scene, for extended periods of time the last three days, their claims not being hotly contested yet because there are still more boxes than males. But at least one female is in the area and whenever she approaches all sorts of commotion breaks loose. Each male starts some combination of chattering, wing-waving, flying to the box entrance, or chasing. So far the female or females have simply flown about over the grid and haven’t been seen perching on boxes with males or peeking in the entrances, but it won’t be long before these behaviors will occur, signaling that pair formation has begun.
Below is an aerial view of the grid field. Each red dot represents a nest box, and boxes are spaced between 120′ and 150′ apart. They could be set closer, 100’ or even a bit less, but I think the increased distance reduces bickering among pairs. Notice that the grid is far from buildings, woods, hedgerows, and water. This placement is deliberate, to limit chances that predators like cats and raccoons will discover the boxes and to limit competition from House Sparrows and House Wrens, which avoid such exposed conditions.
Post 7, March 22
More Warmth And More Swallows
The record warm spell just keeps on coming. Almost 80 F yesterday with bright sunshine, and today’s a carbon copy. But unlike yesterday the number of Tree Swallows at the project today has almost doubled. Newcomers must have ridden in on the warm breezes, the first additions in several days. I counted 12 this afternoon. They alternated between either swirling about in a rather tight flock foraging (I think) on a swarm of small flying insects, or charging around shrieking and calling and chasing over the boxes as groups of Tree Swallows typically do in early spring. However, once again today was different from yesterday. While yesterday males perched alone at several boxes, today there were pairs at both boxes 1 and 2, each with two swallows perched. These pairs displayed defensively when other swallows passed. However, they hadn’t yet reached the stage of mutual tolerance where they would perch on the crossbar together. Instead, one would perch on the bar, the other on the box or at the entrance hole.
I’m never certain whether the first pairs formed each year are birds that nested here previously and arrived back at the boxes, recognized each other and overcame hostility almost immediately, or whether one or both are strangers that knew a good situation and partner when they saw one, and decided not to waste any time. When pairing occurs so very fast, as the swallows at boxes 1 and 2 seemed to have done, I’m inclined to believe these particular swallows “have a history” stretching back one or more nesting seasons, and have reunited at Salmon Creek. Perhaps they were paired here in the past, or were neighbors, already familiar with each other. Perhaps one or both have used this same box before. It’s not impossible that they came north from the wintering grounds together and homed on this very box. Each one of these birds is an individual with a unique life history of individual events. It’s always a bit profound to wonder which of these swallows is a return that has watched me for one or more years, that “knows me” in a sense. Some certainly have seen me many, many times. A few of them I’ve known since they were eggs!
Just as I was leaving a chorus of Tree Swallow alarms rang out and every swallow burst into flight and climbed up and away to the north. I looked around for the inevitable cause and after a bit of searching spotted a Sharp-shinned Hawk flapping and gliding several hundred feet up. There had been a steady flight of Turkey Vultures all the time I’d been there, drifting across the sky like great boats. But the swallows paid the vultures no mind – they never do. However, the Sharpy, an ambush predator on birds, caused an instant reaction from the Tree Swallows even though it seemed clearly, to me at least, to be in migration mode, not on the hunt. By the way the Braddock Bay Hawk Watch tallied over 1900 hawks, falcons, vultures and eagles yesterday.
Post 8, March 27
It had to happen. The record warmth has gone and it may be weeks before we see 70’s again. Friday, 3/23, didn’t get out of the 50’s, with solid overcast and a few raindrops. The pair at box 1 were the only Tree Swallows seen during my brief morning visit to the field. They were largely silent with only occasional gurgles or a quick song. They completely ignored a Northern Harrier coursing low over the field. I saw no flying insects, but there may have been some in sheltered areas along the creek. For the swallows’ sake I hope so.
Saturday, 3/24, began with light rain. It was cloudy again all day, and once again never climbed out of the 50’s.
Today, 3/25, was more of the same. Cool with misty drizzle and a wind out of the NW. There were no swallows at all at the grid. I assume they’ve moved to a sheltered area or areas somewhere in the Braddock Bay wetland complex where they might be able to find a bit of food. I don’t believe Tree Swallows reverse migrate south when facing cold conditions in spring. Instead, they stay put in the general region and try to tough it out. Unfortunately, the next two days are going to be even worse here, with highs only in the 30’s, and dipping tomorrow night into the 20’s. This is actually the norm for this area in late March. These swallows may pay the ultimate price for arriving so extremely early.
Below there’s a shot taken from Google Earth showing some of the prominent bodies of water and land forms near our box project. The Salmon Creek Grid’s location is in red print.
For a quick YouTube video of the grid taken today, 3/25, see below:
Post 9, March 26
Fighting to Live Through the Cold
It was cold this morning! Well actually it was normal for this time of year in upstate NY, but we’ve been so spoiled lately that this morning was a shock to the system. At the field there was a strong wind blowing directly out of the north off the lake that, when combined with an air temperature of about 30, produced a wind-chill effect of low 20’s. Brrr! I had the foresight to dress warmly but this option wasn’t open to the swallows. They had to resort to other tactics.
This little group of swallows is in for another rough day or two. The cold and wind have lasted all day, and with a clear sky tonight a hard freeze is expected, with temperatures dropping into the low 20’s. Although there should be some sheltered spots along the creeks and ponds I don’t expect there were insects flying today. So these swallows will need to rely on whatever reserves of energy they’ve been able to store in their bodies during the warm spell to provide fuel to keep their metabolic engines going until they can feed again. If they run out, they will die.
But Tree Swallows are pretty resourceful little critters. Those in the photo above have found a spot where wind chill wasn’t a factor. They are down on the ground where the temperature of the earth is several degrees higher than the air above. And they are in a place where they can use sunlight to warm themselves a bit, but every bit helps when you are in survival mode.
Tonight I’m fairly certain this little group of swallows will all roost together in a cavity, packed together tightly to conserve heat. Many cavity-nesting birds do this when necessary; bluebirds, chickadees, and some wrens all do. I’ll never forget the time years ago I was making box checks after a very cold night and upon opening one box found it stuffed to up to the entrance hole with swallows. This was in mid-morning when I thought any swallows would be done roosting, but during extreme cold they’ll apparently stay balled-up in a group all day in a box. There couldn’t have been less than 20-30. They hardly stirred. It’s possible they were in a state of “torpor” where their metabolisms had been lowered to reduce rate of energy loss. In any event I was able to re-close the box, but since then I always open boxes just a crack after cold nights to avoid disturbing roosting birds that might be inside. I’ll be very careful tomorrow morning.
Post 10, March 28
Looks Like They Made It
Yesterday, 3/27, was cold! When I checked the thermometer at 6:00 AM it said 24 degrees, and there had been a hard freeze overnight. Fruit-growers all across western NY must have had a sleepless night; I expect crop losses due to bud damage will be severe. Apples, cherries, and wine grapes are important crops in our local economy.
I made a fast trip out to the boxes. The sun was very bright but a cold wind out of the NW cut to the bone. 6 Tree Swallows appeared briefly but showed no interest in the boxes as they headed quickly for the bay. Perhaps they’ll find a hatch of aquatic insects. After checking the boxes, I left almost as quickly as the swallows; no sign of overnight roosting and no dead birds, thank goodness. It’s not supposed to pass 40 F today, but tomorrow is forecast to hit the 60’s. Can’t wait!
Today, 3/28, began with a little sprinkle but almost immediately afterward the sun broke out, the wind swung SW, and you could feel the temperature climb minute by minute. I hurried out to the field and was very happy to hear the shrill cries of excited Tree Swallows as I neared the boxes. Looks like at least most of them made it! While yesterday was a “survival day,” today recovery is in full swing. At 9:00 AM the temperature was already in the high 50’s, with bright sunshine. The only drawback was the wind, growing in strength.
Unlike yesterday when the emphasis was on finding food and staying warm, today there was much interest in the nest boxes. There was hardly a moment when there wasn’t a chorus of chatters and shrieks from the 15 or so tree swallows dashing about the field. At one time or another every box had two swallows perched on it, as females moved from box to box checking them (and males) out. And today for the first time this season a few tentative pairs had overcome their mutual aggressive tendencies and perched together very briefly on the bar.
Another typical early season behavior I saw frequently today was “peeking in.” The importance to Tree Swallows of cavities in which to nest cannot be overestimated, but there always seems to be a certain amount of apprehension involved at first. A swallow will perch at the entrance hole and tip its head slightly forward to peek in without entering. Perfectly understandable, I think. After all there could be dangerous things inside – snakes, squirrels, mice, etc. In later weeks they will duck inside with no hesitation, but not yet.
Post 11, March 31
Yes, They Are Tough Critters
3/29 was what I would normally consider a typical late March day in upstate NY. It never got out of the 30’s, and was cloudy all day long. Pretty grim in general, so I stayed away from the boxes. I didn’t really think the swallows would be there anyway. Hopefully they’ve found a sheltered spot along one of the creeks where some hardy aquatic insects are hatching.
3/30 was downright cold at the start. The home thermometer read 28 F at 8:00 AM. By 10:00 AM it had climbed into the 30’s and there were a few breaks in the clouds so I headed to the field. In spite of a strong NE wind off the lake there were roughly 15 Tree Swallows about the boxes acting territorial, so they must have managed to find enough food yesterday and earlier this morning to allow this behavior. At various times pairs sat together on the perching crossbars of boxes 1, 5, 6, and 8, so the pairing process continues when the weather permits.
A lone male was trying to claim both box 3 and box 4, flying back and forth from one to the other, and chattering and displaying at the entrance whenever another swallow approached. Although in some situations where boxes are rather close a male can successfully hold two boxes, I deliberately place my boxes too far apart to permit this. Not once in the previous nine years has a male been able to claim and hold more than one box here. I want their later attention focused on supplying food for one brood of young and one brood only.
3/31, the last day of this strange month has arrived. I can’t wait to see the month’s weather summaries. I expect there will have been new records set for average warmth and lowest snowfall.
We were supposed to have 1-3 inches of wet snow last night but all we got were a few wet flakes that melted on contact with the ground. However, it was still cold, as it had been for the past several days. It was in the low 30’s with heavy clouds and a strong NE wind in the morning. Plus, all the vegetation was damp. A bad day to be a Tree Swallow that came north too early. I stayed away from the field until 3:00 PM, when the sun suddenly broke out over the lake.
There weren’t any Tree Swallows at the field, but I wasn’t really expecting any; this is definitely a survival day as opposed to a box claiming and pairing up day. However, I did make a round of box checks and as I suspected found clear signs of communal roosting. The floor of box 7 had a fresh coat of “whitewash” and even a couple of tiny body contour feathers matted in the feces. Of course, there’s no of telling how many swallows balled together to conserve heat in this box last night, but I hope it was the whole little band of tough critters.
Post 12, April 1
A Bad Day to be a Tree Swallow
I had hoped today would be decent. After all the sun had come out late yesterday, and I’d even seen some flying insects in my back yard. But this morning was dismal to say the least, with a solid gray sky, temps in the low 30’s, and a drizzling rain mixed with sleet, and today there was to be no let up. At least there was no wind – wind combined with cold and wet can be a killer of aerial insectivores, birds that rely on flying insects for food.
There were no swallows at the field during my morning visit for the second day in a row, and driving around scanning the wetlands from the car yielded none either. Of course, there were many places where the swallows could potentially be foraging that I couldn’t view, but my concern for their survival is mounting. There have been rather poor conditions for an extended period of time now, broken occasionally by a few hours when I think they could find food. How successful they are in refueling during these brief favorable intervals may determine whether the swallows will live or die. Tomorrow’s forecast is calling for slightly warmer temperatures and lots of sun, thank goodness!
There was no sign that any of my boxes had been used for communal roosting last night. They probably piled into one of the many wood duck boxes that dot the cattail marshes.
Post 13, April
Sunshine and Swallows!
What a relief! Awakening to a frost and temps below freezing just heightened the apprehension that had been building in me over the last few days that the little group of super-early Tree Swallows that had been attracted to my nest box grid might have succumbed to the cold, wet and wind we’ve been experiencing. After all, I hadn’t seen them for over two days. You’d think after all these years I’d know better, but I guess I underestimated the resilience of this species once again, for with this morning’s bright sunshine the swallows had come back to the field. Given a bit of food once in a while these guys know how to deal with the cold. For instance, each one I saw perched was puffed and fluffed, holding a layer of insulating air between its feathers to reduce the chilling effect of the north wind.
As the morning warmed there was further proof that they really were ok, for box claiming and pairing behavior went into full swing, with cries, chases, songs, flutters, etc. throughout the grid. If you’re interested here’s a quick YouTube video of the chatter call pairs use to defend boxes they’ve claimed:
There were clearly pairs being formed – at one time or another almost every box had two swallows perched close together on a bar.
And every once in a while one, most likely the female, would duck inside a box to check things out.
But the biggest surprise came when I made a round of box checks. While every other box was totally empty, there inside Box 5 were several pieces of dried grass! This beginning stage of nest building is far and away the earliest in all my years with Tree Swallows. This continues to be a year of the unexpected. I can’t wait to see what’s next!
Post 14, April 3
The March weather data for the Rochester, NY area have been posted and to no one’s surprise several incredible new records were set. There were 18 days with temps 60 or more, and between the 17th and the 22nd highs reached 70 or better! And most amazing of all the average monthly temperature was 47.5, a staggering 13.5 degrees above normal! I assume many other places in the NE reported similar records. No wonder tree swallows and many other migrants came north so early. But not all tree swallows did. Some waited.
Today, for the first time in two weeks, there were more than 20 Tree Swallows at the field. A new bunch must have come in yesterday after I checked. Actually, these swallows are right on time, for this is when, in a “normal” year, I would start hoping to see my very first swallows! Of course this sudden influx of new birds caused all sorts of commotion at the grid. Established pairs from the first wave of swallows were raising a din of shrieks and chatters defending their boxes as the new birds flew from box to box prospecting, as you can see in the video below.
I wonder if these newcomers will be able to displace at least some of the early arrivals from their boxes. I wouldn’t be surprised. They should be in better physical condition since they haven’t had to cope with the rather crummy weather we’ve had here for the last week.
Over at Box 5 the female had added a few more bits of dried grasses to the beginning of her nest. All seven other boxes were still completely empty, as they normally would be this early in the season. The Box 5 female obviously feels very secure with her box. Unlike most of the other females she was spending considerable time inside or peeking out her entrance today.
Post 15, April 4
The Intraspecific Competition Increases
Today was sunny and seasonal, with morning temps in the 40’s. A medium breeze blew from WSW, not off the big lake for a change, thank goodness.
Every one of the eight nest boxes had a pair of Tree Swallows in attendance, but there is now a large surplus of birds to boxes – 25-30 swallows were at the grid this morning. The newcomers moved from box to box in small groups, causing the established pairs to break out with the usual chattering, shrieking, wing-waving, gaping and chasing. A Tree Swallow project grid sure can get noisy at this stage in the nesting cycle! I just sat back in my old lawn chair and enjoyed the action. I like to watch from what passes for the high ground, a slight rise near box 2, and each day I move the chair a bit closer to the box. Today I was about 20′ away, but as time goes on I’ll ease in to within 5′ or so from the pole. One of the real joys of having tree swallows is that as they learn I’m completely harmless they begin to treat me as if I’m not there at all, unless of course I make a sudden move. All the pictures below were taken from the comfort of the chair. The series shows one pair dealing with intraspecific competition from another pair for a crucial resource, a nest cavity. And after the photos there’s a link to a video of some of the competition. Check it out.
And here’s the video of some of the action:
Post 16, April 5
Correcting A Mistake
In yesterday’s original post I made an embarrassing mistake: I stated that “interspecific competition among Tree Swallows is increasing” at my grid. Thanks to ornithologist Tim van Nus of the Netherlands, who called my mistake to my attention, I have corrected the post to: “intraspecific competition among Tree Swallows is increasing”, not interspecific. And since I didn’t get a chance to visit the swallows today and don’t have anything new to report, I thought I’d take a moment to discuss how intraspecific and interspecific competition are different.
Intraspecific competition occurs when two or more members of the same species contend for something. For instance, in recent posts I’ve been describing some of the ways Tree Swallows compete with other tree swallows to claim what is for them a vital resource, a cavity to nest in.
Interspecific competition occurs when members of different species contend for something. I haven’t described this because my boxes are placed way out in a field where potential competing species don’t want to nest, so the swallows at my grid haven’t faced any interspecific competition for resources.
However, interspecific competition for nest sites is a very real issue for cavity-nesting birds like Tree Swallows that are unable to excavate their own cavities. For instance, in some situations tree swallows find themselves competing with bluebirds, Purple Martins, House Wrens, or House Sparrows for nest sites. Luckily, sometimes there are things you can do to reduce or eliminate the strife.
Since I’ve elaborated on interspecific competition on my web site www.treeswallowprojects.com I’ll simply give you links to those pages if you want further information or suggestions for competition reduction. See below:
Tree Swallows versus Bluebirds: www.treeswallowprojects.com/tresvsbb.html
Tree Swallows versus Purple Martins: www.treeswallowprojects.com/pmartin.html
Tree Swallows versus House Wrens: www.treeswallowprojects.com/wrendam.html
Tree Swallows versus House Sparrows: www.treeswallowprojects.com/spardam.html
Tree Swallows versus Tree Swallows: www.treeswallowprojects.com/cboxclam.html
Post 17, April 6
An Experiment Begins
This morning, 4/6, was pretty typical of our last week weather-wise. It started cold, with temps in the 30’s, after a frost last night. A bright sun shone but its potential warming effects were blunted by a bitter wind directly off Lake Ontario. It should be tough for Tree Swallows to find food under these conditions, so what better time to begin experimenting with a prototype tree swallow feeder.
For years I’ve thought how nice it would be to offer food to Tree Swallows during extended periods of cold, wet, windy weather, and have them accept it. It would be especially valuable if parents could learn to take supplemental food to their young, thus reducing their brood’s risks of stunting or starvation. Supplemental feeding has already proved very effective with some other cavity-nesting birds that are primarily insectivorous, especially bluebirds. And since at least some individuals of our biggest swallow, the Purple Martin, have learned to accept foods provided by humans, I finally decided if martins can do it why not try offering food to Tree Swallows?
As you can see the feeder’s design is very simple. A small plywood cube with “entrance holes” in all four sides sits in a wooden tray with shallow sides. Food items can be placed in the tray’s bottom, and hopefully Tree Swallows will be attracted to the cube as though it was a nest site, perch on it, see the food items, and eat. Today, I decided to offer live mealworms, which are actually beetle larvae, and which can be bought at many pet stores. Of course, these are quite different from a Tree Swallow’s normal flying insect food, but since they will sometimes pick non-flying insects off the ground, I hoped the swallows might learn to take mealworms crawling in the feeder trays.
Since there are now about 30 Tree Swallows hanging around my eight-box grid there was an immediate reaction to what appeared to them to be a new box. By ones, twos, and then larger groups, swallows began milling about the feeder and eventually landed on it.
But it was clear from the start that the swallows’ interest was strictly on the feeder as a potential nest site. All the typical box-claiming behaviors took place: chatter, wing-waves, display at the holes, etc. And although I did see a swallow or two cock its head and seem to look down at the mealworms, in an hour and a half of watching I didn’t observe a single mealworm being eaten.
After I became so cold I started to shake I decided to end today’s experimental session. I removed the whole apparatus and will present it again and again on future days until I’m convinced it’s had a fair trial. I hope sooner or later a Tree Swallow “savant” will figure out there’s an easy meal to be had here, and others will observe and get the message. Plus, I’m sure the design can be tweaked if this configuration fails. Perhaps wider trays and lower sides would be better, for instance, and perhaps the entrance holes are too distracting and should be covered over. Lots of things to try. Also, the mealworms were so cold they didn’t squirm about, so perhaps they’ll “perform” better under warmer conditions. Freeze-dried crickets are another option. Since I think training a population of Tree Swallows to use a feeder would be important from a management standpoint, I’m going to keep on trying in the weeks ahead. So, you’ll be hearing more on the feeder experiment in the days to come.
Post 18, April 8
Things Seem To Be Settling Down To “Normal”
Once again, we have bright sunshine, temps climbing from 30’s into the 50’s, and a cool breeze off the big lake, a pretty common set of conditions for early April here at Salmon Creek. This return to “normal” weather has been mirrored by a return to a “normal” schedule by the Tree Swallows at my grid. The extremely early migration by some of the birds was followed by early box claiming and pairing, but the next major step in the cycle, nest building, is taking longer to commence. In fact, it seems nest building is right about where I’d expect it to be on this date, based on the past nine years’ data, that is to say it hasn’t really begun yet.
You might think since Tree Swallows are in such a hurry to claim nest sites, they’d also be in a rush to get their nests built, but there’s almost always an early season lag between box claiming and nest building. Box checks made every day this past week tell the same story. Boxes 1,2,4, and 8 are completely empty. There are single pieces of dried grass in Box 3, 6, and 7, and after the initial fast start in Box 5 nothing has been added since the 4th of April. In most years nest building doesn’t begin in earnest here until at least the second week in April, so it seems this year’s cycle is slowing down to a more normal pace after the jack-rabbit start.
I do think that some of the females are on the verge of building though. The single pieces of dried grass in some boxes hint at this. And as I sat next to Box 2, I watched the female repeatedly sail out low to the ground, flying slowly and peering down – just the way females do when they intend to drop to the ground to pick up nest vegetation – except she didn’t complete the behavior. However, it shouldn’t be too many more days before she does.
Pairs were generally quiet at the grid today, perching on the bars together or flying out a short way to pick off a flying insect or two. However, when the swallows without nest sites, ones ornithologists call “floaters,” intruded, I noticed the squabbles are becoming more intense. Real fights are breaking out now, with birds grappling in the air, and occasionally locking together and tumbling to the ground. Swallows thrashing at each other on the ground usually draw a crowd of calling spectators, so it’s easy for me to tell when one of these tussles is going on, even at the extreme other side of the grid. In other years I’ve sometimes been able to walk up to fighting Tree Swallows, grasp and separate them so they wouldn’t injure each other. There are 10-15 floaters still hanging around, so there was usually an uproar somewhere in the grid, and the wave of second-year swallows hasn’t even arrived yet. It will really get lively when they do!
Post 19, April 10
A Possible Reason For No Bluebirds At Salmon Creek This Spring?
Yesterday morning, 4/9, was brutal at the grid field: solid gray overcast with a strong west wind that blasted me as I walked out to the boxes. The swallows must not have been thrilled by these conditions because they were nowhere in sight. Even perching on the crossbars would have been difficult, so there was no point for them to be territorial, or to even be present. I assumed they had adjourned to more sheltered locations in the wetlands to forage for food. I didn’t even make box checks for fear the wind would blow grasses right out opened doors.
I did get one thing accomplished though. I removed the bluebird box I’d put up adjacent to the hedgerow in the field a couple of weeks ago. A bluebird pair had been hanging around the neighborhood in mid-March, and I’d hoped they’d accept a box if it was placed a relatively short distance from hedgerow shrubs and trees to perch on. However, no bluebirds have been present recently in the vicinity of the field, and I think I know why. You might guess that all those Tree Swallows have driven them off, but this isn’t likely because pairs of bluebirds often successfully claim boxes and raise broods within Tree Swallow grids. I’ve had Eastern Bluebirds nest within three of the four swallow box grids I operated prior to Salmon Creek. Bluebirds aren’t the gentle pacifists some people would have you believe they are, far from it! Bluebirds can and do attack and kill other cavity-nesting birds, including Tree Swallows, chickadees and yes, even other bluebirds. No, I think the bluebirds moved on because a pair of American Kestrels has been patrolling the hedgerow and hunting the mowed fields on the far side. These beautiful birds, our smallest native falcon, are rapidly declining in eastern North America due to habitat loss as small farms are converted to large farms, suburbs, or return to forest.
Kestrels are certainly welcome here at Salmon Creek, where the hundreds of acres of fields offer good foraging, and nest sites are available in old barns and wood duck boxes nearby. I don’t believe the Kestrels will endanger my adult swallows, but later on they could pose a threat to inexperienced just-fledged juveniles. We’ll see. The Kestrels won’t let me anywhere near them, so I have no Kestrel photos for you. However, if you take this link to the photograph sharing web site Flickr, you can view many great shots of this elegant cavity-nesting little raptor: http://www.flickr.com/search/?s=rec&w=all&q=american+kestrel&m=text.
Post 20, April 12
Tree Swallow Feeder Experiment #2
After watching the experimental Tree Swallow feeder (described on Post 16) over several days I made the following observations. The swallows were only reacting to it as though it was a potential nesting site. These birds have their priorities, and they totally ignored the mealworms in the trays, even on very cold mornings when I would have thought they would be highly motivated to eat. Perhaps the problem was that the mealworms weren’t recognized as food items, but I haven’t found a local supply of freeze-dried crickets yet to substitute. And the swallows that landed on the feeder all seemed to be floaters, birds seeking a nest site, rather than paired birds already in possession of a box. So, going back to the drawing board, I made a couple of simple trays that could be fastened temporarily to the pole of a nest box.
You might think hooking something new like this next to their box would upset the swallow pair, but within a minute or two they were perching on it or near it as though it had been there forever. But even though the mealworms were there in plain sight within a few inches of the swallows, they were completely ignored by the pairs at boxes 1 and 2, where I tested the trays today.
This round of tests is convincing me that mealworms really are too alien to be recognized as a food source by Tree Swallows. I’ve got to get some crickets soon, but once again, crickets are not something a Tree Swallow would be apt to capture in flight. I would have though these birds had a flexible “prey recognition program,” but perhaps I was wrong.
The focus of the Tree Swallows at the grid this morning was clearly not on eating. Instead, it was on either finding a nest site if you didn’t have one yet, or preventing floaters from intruding at a nest site you’d already claimed. These preoccupations overrode everything else during the time I watched. They really seemed completely oblivious to the feeders. So, it’s either test other foods or wait until the swallows are more intent on finding food, as they will once they have nestlings to feed. The trials will go on. I’m not giving up yet.
Post 21, April 13
When Is Nest Building Finally Going To Start?
Well, it’s been almost exactly one month since the first Tree Swallows arrived here at Salmon Creek, and I first began to notice paired birds at boxes on 3/22. But, while nest site claiming and box defense have been pretty much non-stop except when bad weather kept the swallows away searching for food and shelter, day after day box checks have shown very little evidence of nest building. Shouldn’t one think they would have started by now, after 3-4 weeks at the project’s box grid? Actually, the answer is no, a delay of this kind is very normal for the Tree Swallows here. Checking my records for Salmon Creek I find that nest building in this species seldom begins in earnest here until mid-April, and occasionally even later. It appears that the record early arrival of Tree Swallows in March did not automatically mean there would be record early nest building.
Perhaps the past week plus of cool weather, with bitter lake winds, has slowed things down. Perhaps the swallows haven’t been finding enough food yet for their hormonally driven metabolism to trigger the next stage in the reproductive cycle. Or perhaps the start of nest building is governed by the length of the day, which is the same each year. I wouldn’t be surprised if all these come in to play in varying degrees. There’s still a great deal we don’t know about wildlife, even regarding a species that’s been studied as much as the Tree Swallow has.
(To learn how valuable Tree Swallows are in ornithological research see http://www.treeswallowprojects.com/resch.html)
Whatever the reason for the annual delay, I think things are about to change. We expect a push of warm air in the next few days, which should increase the swallows’ food supply and perhaps stimulate nest building. I suspect the females, who will be doing the work after all, must be near the threshold for gathering the dried grasses that will make up the nest base and cup, and as I sat in my traditional spot next to Box 2, I saw a swallow go in and out of Box 3 twice. And when I checked the boxes I found the situation below. Where yesterday there was only one lonely piece of grass in Box 3, today the number had increased substantially. It may not look like much but this female has really begun to build, and since Tree Swallows nesting in loose groups, as in my grid, tend to be fairly synchronized in their nesting behavior, I predict other females will be building very soon. Come on ladies, let’s go!
Post 22, April 14
Math Is Dictating Much Of The Behavior Now
Finally, a day with a gentle warming south-west breeze. It was a great morning to be outside. The air felt “soft”, and you almost could sense the field plants growing. Insects were flying too, so today the swallows were able to do a lot of their foraging over the field itself, instead of flying to the nearby wetlands for a bite to eat. However, in other respects, the behavior exhibited by the Tree Swallows at the grid hasn’t changed much with the weather. It’s pretty simple math, really. With eight boxes and over 30 swallows whose purpose in life is to reproduce, we have a classic shortage of a critical resource. The supply of boxes is low but the demand is high, very high. So there are two categories of birds at Salmon Creek at the moment: paired swallows that possess a nest box, and unpaired “floaters” that need a nest site, and the category you’re in determines what you must do.
Pairs possessing boxes, like the birds at the box below, must be constantly on guard, ready to use calls, physical displays, chases, and if need be fighting, to repel intruders that want to take their nest cavity.
Floaters must search for nest sites, and if none are vacant, they must intrude on occupied ones, probing for signs of weakness in the current owners that could signal a chance for a successful takeover.
So, the pattern of the last two weeks continues. Pairs defend their boxes and floaters roam about intruding and testing for weakness. Occasionally fights break out and swallows tumble to the ground locked in battle. This is a serious business. And sometimes a floater is successful, taking over a box and often inheriting the previous owner’s mate. I’m pretty sure this has already taken place at least once this year.
If this is the situation now at Salmon Creek, and the habitat can support many more Tree Swallows, as it certainly could, wouldn’t it be a good thing to add more boxes so there will be more to go around? Actually, this is just what I plan to do, but not yet. I’m holding six boxes in reserve, but will wait to put them up until the swallows have sorted out who’s the toughest, and the winners have built nests and begun to lay eggs. I’m doing this because I hope to see which of two recognizable age classes of Tree Swallow females using the late boxes raises more young on average, older females or young females in their first nesting season. More on this later. In the meantime if you want to see how to distinguish younger female Tree Swallows from older females enter the web page URL below in your browser: www.treeswallowprojects.com/csexage.html.
Post 23, April 15
Second-Year Tree Swallows Have Arrived
This morning, 4/15, dawned mild but very gray. Since showers and possible thunderstorms were in the forecast, I got an early start and headed to the field. It was the “same old” there with one exception. The number of Tree Swallows has increased again – it’s closer to 40 now. Perhaps yesterday’s warm front brought in a fresh wave of migrants. I think this is the case because something I wait eagerly for each year has happened – “second-year” Tree Swallows have arrived.
Before we get too far into this here’s a quick explanation of some terms. Second-year swallows are birds that are now in their second calendar year of life. The ones I saw today hatched last year, and are in their second calendar year now, even though they are actually less than one full year old. This will be their first nesting season.
Older, after-second-year swallows are in their third, fourth, fifth, etc. calendar year of life. They have already been alive during at least one nesting season, and may have already nested one or more times in past years.
As I write I’ll sometimes refer to second-year birds as SYs, and after-second-year birds as ASYs. Bear with me on all this, it’s actually pretty interesting.
As with many other bird species, different age classes of Tree Swallows migrate at different times. Older tree swallows move north first. These ASY birds are the ones that began arriving in March and are the ones that have been at Salmon Creek for weeks already. But SY Tree Swallows don’t usually arrive here until mid-April, so they’re right on schedule this year.
How can you tell SY Tree Swallows from ASYs? Well, with males you can’t – the two male age classes are identical in appearance. But Tree Swallows are one of the very rare bird species in which only female SYs have a unique, differently colored plumage. Instead of the beautiful iridescent blue head and upper body that all adult males and ASY females show, SY females are brownish with a few green highlights. If you are curious about this enter the web page below in your browser. It includes some nice photos illustrating the age and sex differences in plumage. Anyway, to make a long story short I was able to tell SYs had arrived at Salmon Creek because today I saw a couple of brown females. Here’s the web page URL: www.treeswallowprojects.com/csexage.html
These SY newcomers were doing just what you would expect because their “goal” is the same as the older birds’. They want to reproduce, and since there are no available nest boxes at the project grid the SYs have joined the pool of floating ASYs, intruding on box-owning pairs, hoping to take a spot. The male SYs will try to kick out the male of a pair, and female SYs will try to oust paired females. That’s right; females will fight females if they have to, sometimes fiercely, because females absolutely must have a nest cavity in order to reproduce. Males have another option, as we’ll see later.
I know today’s photos are pretty dingy due to the overcast, but trust me, the bird on the right in the photo above has a nice chocolate brown back and head. Next year, after molting, they will be blue. And if you look closely, you’ll notice she also shows just a hint of a breast-band, another sign of her younger age. You can see this somewhat better in the shot below.
You may wonder why such an odd situation exists, where only females have a different plumage, and only have it for one year of their life. I wonder too. I’ve given this a lot of thought over the years and believe that since it’s so unusual there must be an “out of the box” explanation. I think that for a very brief period of time, and only in their second year of life, there is an advantage for these young females to look different. I’ll share my reasoning with you when we begin the reserve box experiment at the start of egg laying.
Post 24, April 16
Warmer Weather But Still No Nest Building
Today was another beautiful warm spring morning. Temps were in the 60’s already and headed for 80! There was a moderate south wind and cloud cover was present but high. The conditions were excellent for birds that migrate in day-time and at 8:30 AM Broad-Winged and Red-Tailed Hawks were already streaming over from west to east. It will be a great day at the Braddock Bay Hawk Watch. Flickers were moving through the hedgerow, and closer to the ground Red Admiral Butterflies were everywhere.
The round of box checks today has yielded an answer to the question whether this burst of warm weather would stimulate an immediate burst of nest building behavior by the paired female Tree Swallows at the Salmon Creek box grid. The answer is no. The nest status has hardly changed during the last several days. Boxes 1,2, and 4 remain completely empty. There is one piece of grass in Boxes 6 and 8. Boxes 3, 5, and 7 have a bit more nest material but still less than 10 pieces each. And I strongly suspect that the female who put the early grasses in box 5 two weeks ago is no longer in possession of Box 5. If she was I think more material would have been added by now, but none has since 4/2. The original female may have died during the cold snap, or may have been displaced by another female. It happens.
So, in spite of the fact that some Tree Swallows have now been present at Salmon Creek for more than one month, nest building hasn’t really begun. This may seem odd but my records show that they are actually just where I’d expect them to be at mid-April. Perhaps the nest-building part of their reproductive cycle is rather “conservative”, more ruled by fixed aspects of their environment like gradual day length change, rather than temporary weather ups and downs.
However, there was one noticeable change from yesterday: fewer Tree Swallows. In 24 hours the total dropped from over 40 down to 30 or slightly under. My guess is that yesterday’s high count included a curious group of second-year birds heading farther north and east around Lake Ontario. But there was still one brown SY female today, so at least some second-year birds have lingered at the grid.
So, what were the swallows doing if not nest building? The usual: pairs guarded and defended their boxes; floaters prospected and intruded. And all kept a wary eye on the American kestrels hunting nearby. When there were lulls in the action both groups of swallows, box owners and floaters, foraged for flying insects over the field. Pairs often took advantage of quiet moments to preen their feathers while perched on their crossbars. Floaters did the same as they perched on plant stems in the field. As you can imagine taking care of one’s feathers is a very important activity for a bird, especially a species that catches most of its food while flying as Tree Swallows do.
There’s more on feather care at this web page,
and you can watch a short video of Tree Swallows preening below.
Post 25, April 18
A Monster Day For Raptors At Braddock Bay
In my post of two days ago, 4/16, I speculated that because of the very warm push of air on strong south west winds the Braddock Bay Hawk Watch was going to have a good day. What an understatement! The official Hawk Count totaled 37,145 hawks, falcons, eagles, vultures, etc., with representatives of 15 different species! The vast majority were Broad-winged Hawks (34,243) migrating north from Central and South America. And a new one hour record was set: between 11:00 AM and noon 22,375 raptors were tallied, an absolutely mind boggling number! Trust me; to be on the platform on a big day like this is something you’ll remember for the rest of your life.
This monster day included 43 migrating Kestrels, so it was no surprise that I found no less than six Kestrels the next morning hunting the fields surrounding my swallow box grid. These probably included the pair that seem to be local residents, plus some others that lingered after the cold front arrived late on the 16th, shutting down the migration temporarily.
Make no mistake, I love Kestrels. The Tree Swallows, however, aren’t so fond of them. They were obviously keeping their eyes on these elegant little falcons. The latter spent most of their time moving from place to place above the fields, hesitating briefly to hover and look down for prey, then either moving on or dropping down to the ground for a capture. I couldn’t tell what they were catching but the prey items had to be small, less than mouse sized. Kestrels do eat many insects, so perhaps they were chowing down on insects numbed by the morning cold.
Whenever a Kestrel got a little too close or moved a little too quickly the Tree Swallow response was dramatic. A first alarm cry quickly would become a chorus, with every swallow rising high in the air, milling about and screaming. It appeared the swallows wanted to be higher than the kestrels, so the kestrels would not be able to dive upon them from above. They clearly viewed the kestrels as potential danger, although the kestrels didn’t appear to be interested in them, at least not at the moment. However, worldwide, several species of small falcons are well-known for their ability to catch and consume swallows, for although swallows can fly extremely fast, Merlins, Hobbys, Kestrels and Peregrines are faster still.
In a possibly related observation, I found that the female Tree Swallows at my box grid had not gathered any more vegetation for their nests, none on the 16th and none on the 17th. Could the presence of all those kestrels be inhibiting them? Perhaps the swallows are reluctant to land on the ground trying to wrestle pieces of grass loose, knowing a kestrel could be watching from above. A swallow down on the ground or in thick vegetation is a vulnerable bird.
Post 26, April 19
Tree Swallow Feeder Experiment #3
One of the great joys of going outside is you never know what to expect. It seems every day holds fresh surprises if you keep your eyes open and your mind receptive. This morning, 4/19, it was a pair of Osprey in a dead slippery elm in the hedgerow bordering the grid field. One was enjoying an orange-colored breakfast that looked suspiciously like a goldfish. People frequently dump goldfish that are outgrowing their bowls into the local stream and ponds. I’ve seen some moderately-sized ones from my canoe, but never very large – those expect fishermen, the Osprey, see that none become whoppers.
Yesterday and again today I tried once more to see if Tree Swallows would accept potential food items from a feeder. This time shallow trays were mounted at two different boxes each day, and bayberries, canned crickets, and freeze-dried crickets were presented at each box, alone and in various combinations.
Trials lasted roughly two hours each day, all with the same result. Every offering was ignored. The swallows were clearly aware of the food items, but made no movements toward them that could be interpreted as investigatory or an intention to taste or eat. They weren’t the slightest bit inhibited by the feeders, as you can see in the next photo, and by the way can you tell which of the four Tree Swallows is a second-year (SY) female?
This attempt concludes the feeder experiments, at least for now. The swallows seem too preoccupied with box claiming and defense at this time. Maybe I’ll try again later in the nesting cycle.
For many days now box checks have shown no increase in nest building activity. Things are really at a standstill. No females are bringing dead grasses and few are even entering the boxes. But as the number of floating tree swallows diminishes, and the lingering Kestrels move on out, I think nest building is going to pick up. And I expect since the females have been delayed by the same set of factors that when these factors do ease up most of the females will start nest building at the same time. We’ll see if this is true and, if so, just how synchronized they are.
Post 27, April 20
Drama At Box 3
I normally sit next to Box 2, whose pair of Tree Swallows ignores me. They’ve seen enough of me by now to have classified me as some kind of non-threatening creature, as though I were a woodchuck or a cow. But today I decided I’d sit down the row a bit by Box 3, to see how the resident pair there would react.
As soon as I got there, I could see something was wrong. One of the swallows was perching oddly on the crossbar, as though one of its legs or feet was injured. I was able to get close enough to see this bird’s head and back were a slightly brighter, crisper, iridescent blue, which signaled to me that it was a male.
Since I check boxes every day, and pairs seldom fly until I’m quite close, I’d like to believe I’d have noticed an injured or abnormal swallow here before. I’m pretty sure this injury, if that was what is was, is recent, perhaps very recent. Either that or I’m not as observant as I’d like to think.
There is always the risk of injury when Tree Swallows fight over nest sites. Their bills, though small, are sharp. But bills are generally used to inflict injury on the opponent’s head, back or breast. Another possibility is the bird was injured hitting an object as it fell to the ground as it battled with another swallow with legs locked together. The field is studded with stiff broken dead stalks of last year’s vegetation, that could do some damage if hit from above.
I’ll never know for sure what happened, but this swallow is now at a big disadvantage. In addition to dealing with pain, it may now be more vulnerable to avian predators, which are quick to notice and single out injured prey. If it lives and the injury doesn’t heal properly this swallow may have difficulty caring for its feathers and ridding them of parasites. It may have permanent trouble perching on thin vegetation while resting or roosting. It may not be able to copulate, which involves landing on a female’s back and balancing there while making cloacal contact. It may not be able to maneuver through the entrance hole of a nest box, which means it will not be able to feed its young when they are too small to come up to the entrance.
However, perhaps the most immediate issue for this male will be holding on to its nest box, for it will certainly have lost some of its defensive ability, and there are other males floating at the grid that will put him to the test.
Post 28, April 22
Choices On A Dismal Day
Yesterday, 4/21, we were treated to an all-day soaking rain, which in the short term probably meant cold, hungry Tree Swallows. But for the long term the downpour was a good thing because April here has been very dry to date. Some rain now will help ensure lush vegetation and a better crop of insects to feed swallow nestlings down the road in May and June.
However, today has been only slightly better. Instead of steady rain we have steady drizzle. The sky is filled with low gray clouds and the temperature is barely flirting with 40. Although I didn’t visit the boxes yesterday I felt duty bound to go today, and though the usual assortment of Eastern Meadowlarks, Savannah Sparrows, and Red-winged Blackbirds was present in the fields, I only saw one Tree Swallow, and it flew past me to the Salmon Creek channel, ignoring the boxes. This situation at the grid, with no Tree Swallows either guarding or trying to steal the vital nesting cavities, happens regularly during poor early Spring weather, and it made me reflect on what I think is the logic behind some of the choices these birds must make.
Tree Swallows do not defend feeding territories around nest sites the way many other species, such as bluebirds, do. If there is food nearby, great, but if bad weather conditions reduce or eliminate flying insect food near their nest cavities, the swallows must choose: either stay and go hungry, or leave in order to find food.
To me, the decision rests on the need for a swallow to maintain or improve its physical condition relative to its nest site competitors, namely other tree swallows. Let me explain how I think it works for the two groups of Tree Swallows, those possessing nest sites and the floaters who don’t. Here are the options as I see them.
In bad weather, faced with no food near its nest, a box owner can elect to stay and guard its nest, but its physical condition may deteriorate over time from lack of nourishment.
If a floater that leaves to find food feeds well, it may over time improve its condition enough relative to the box owner that has stayed that the floater can come back and take the owner’s box away.
But, if a box owner, that by definition was strong enough to successfully claim a box in the first place, leaves to feed elsewhere, it should at least maintain its superior condition relative to floaters, including those who also left to feed.
And if a floater decides not to leave and feed, but to stay and try to grab a box in the owner’s absence, the floater’s condition will deteriorate relative to the owner that is off eating. And when the owner does return it will give the floater the boot.
So, to me, the logical thing is for both groups, owners and floaters, to put competition for boxes temporarily aside on dismal days and choose to go get food wherever they can find it. And in fact that’s what I usually see; few or no Tree Swallows at field boxes during prolonged cold, rainy spells. Sensible birds.
Post 29, April 24
Box Design Can Affect Swallow Survival
What a contrast! A week ago yesterday, 4/16, we gloried in record high temps in the 80’s. Yesterday and today, 4/23 and 4/24, we got our share of the April “Nor’easter” that hit large areas of the northeast. Yesterday was in the 30’s with rain and wet snow, and today hasn’t been a great deal better, with 40’s, intermittent rain, and cold gusty winds. As I’ve mentioned or implied repeatedly before, this nasty combination forces tree swallows into full survival mode. Box claiming and nest building are forgotten temporarily in the struggle to find food and stay warm. And it’s under conditions like these that little box design refinements may mean the difference between life and death for both adult Tree Swallows and their young.
I stayed completely away from the grid yesterday. I knew there would be no swallows in the field outside the boxes but there might just be clusters of swallows inside one or two boxes, roosting communally to conserve heat. I’ve seen this in the daytime before, and the last thing I wanted to do was disturb them if this was the case.
Today, 4/24, I did venture out to the field, both in the morning and again in the afternoon, but I saw no Tree Swallows perched or flying. They were either roosting or foraging elsewhere over some secluded backwater. I didn’t check boxes for fear of disturbing a roosting cluster. And, as at many other times over the past nine years at Salmon Creek, I was thankful our project’s boxes are made to be snug and dry inside.
Nest box design should take local microclimate into account. If you manage for cavity-nesting birds where hot, dry, sunny conditions are the norm, your boxes must provide ventilation so nestlings inside don’t overheat. But here at Salmon Creek, as I’m sure you realize by now, the microclimatic conditions are very different. Winds sweeping off Lake Ontario often subject areas near the lake to temperatures 10-20 degrees colder than places not much farther inland, not just in spring but well into summer. However, the Long Point boxes we use at Salmon Creek include features to deal with this. For instance, although box interiors are spacious the door openings are quite small, and include wooden baffles that reduce breeze penetration. And there are no ventilation holes near the roof. For us, less air passage is almost always better.
Our boxes are also intended to be as watertight as possible. Roofs hang well over entrances, and the wind baffles also help exclude rain.
And since the boxes are pretty waterproof, they don’t need drain holes in the floor, which, if present, could let in cold air. Plus, we always face our boxes away from the prevailing rain-bearing winds.
So the moral is that it’s not just important to know the requirements of the species one is managing for, it’s equally important to understand how the management setting, the local habitat and microclimate, impact things, and to use this information to help determine the steps you must take to ensure your species’ success.
For more on nest boxes for Tree Swallows see: http://www.treeswallowprojects.com/buildbox.html.
Post 30, April 25
This Is What Starvation Looks Like
This morning was sunny at least, but the temperature was barely 40 and the wind was blowing cold out of the NW when I went to the grid, filled with apprehension over what might be waiting there. That I only found one dead Tree Swallow was somewhat of a surprise, but every death here is saddening, and brings a feeling of defeat. This is why I had hoped for success with the feeder experiments.
I couldn’t determine the sex of the dead swallow in Box 4. It didn’t show a female’s brood patch or a male’s cloacal protuberance – too early in the season. It had no brown feathers above its bill, which a few females but no males show. Its blue feathers were quite bright, suggesting it was a male, but without other evidence I couldn’t be certain. Its legs and feet were sound, so I don’t believe it was the injured swallow from Box 3, mentioned in an earlier post. But there was little doubt in my mind as to cause of death. It had almost certainly starved, a victim of the unholy combination of cold, wind and rain over several days’ time that is so dangerous for aerial insectivores like swallows, martins and swifts. A quick examination was revealing. Parting the feathers of the swallow’s breast I uncovered the keel of the swallow’s sternum sticking out like a knife. What was left of the pectoralis majors, the normally large and powerful muscles so essential for pulling wings down during flight, were shrunken to the point that had this bird been alive I can’t imagine it could have flown.
A weight check supported starvation as the probable cause of death. Tree Swallows in decent condition weigh 20 grams, plus or minus a gram or two. But this unfortunate swallow was down to only 10.2 grams when it died, having metabolized much of its body’s muscle mass trying to survive. Sadly, many other people in the northeast will be discovering dead swallows, martins and bluebirds in the next few days, because if the weather folks are correct the cold spell we’re suffering through is going to linger. Here at Salmon Creek we’re looking at highs in the 40’s and 50’s for the next week, no higher. The swallows really need a recovery day or two, and soon.
For more on Tree Swallow mortality see:
Post 31, April 26
A Recovery Day And A Surprise
What a relief it was to hear Tree Swallows calling as I got out of the car to check the nest box grid this morning. Yesterday, 4/25, it did clear up in the afternoon and evening, and I did see insects flying about my yard, so I had hopes the swallows had been able to find some chow, and recover a bit from the deprivations of the past few days.
Today, 4/26, the recovery seems to be in full swing, aided by somewhat milder temperatures, less wind and some teasing peeks of sunshine. Each box had two swallows in attendance as usual, although the composition of the pairs may have changed due to recent mortality. However, the total number of Tree Swallows, pairs and floaters combined, was noticeably down from last week. Although I had only found one dead in my boxes, it would be naive to think others hadn’t died elsewhere.
I expected no new nest building had taken place, and none had been, but both Boxes 4 and 8 had evidence they had been used for communal roosting during the bad weather – their floors were littered with feces.
I could hardly believe the pleasant surprise waiting at Box 3: against the odds the male with what I thought was an injured leg or foot was still there! I really hadn’t thought it would survive the cold, wind and rain, but there it was, perched as best it could on the crossbar with its mate. Must be a tough cookie!
This time I took a great many photos of him, trying to get one or two that showed the affected leg or foot, so I’d be able to make a better guess as to the cause of his problem. And although my little camera has limitations, I did get a couple of shots that suggested to me that the “injury” was probably a case of Avian Pox, a viral disease that can cause warty growths on a bird’s un-feathered body surfaces. Look carefully at the next two photos: can you distinguish abnormal growths or enlargements on this swallow’s left foot and toes? These look pretty typical of Avian Pox to me but I have to confess I’m not an expert on bird diseases.
Unfortunately, if this truly is Avian Pox, it is not going to get better. This swallow is going to remain limited in what it can do physically, and the condition will probably worsen. And there’s nothing I can do to treat it. But while it’s no consolation for the bird, almost everything that happens at the grid, even a misfortune like this, can present a learning experience for us. For instance, if this male manages to hold on to this box I’ll be very interested in the Box 3 female’s reproductive success, as measured by the number of nestlings that fledge from this box. Will the male’s apparent handicap reduce her brood’s survival? We’ll return to this subject when the mating stage of the Tree Swallow’s nesting cycle arrives.
Post 32, April 29
If Statistics Don’t Lie We’re On The Verge Of “Real” Nest Building
Ok, I have a confession to make. I’ve been getting quite impatient waiting for the Tree Swallows at the Salmon Creek nest box grid to start nest building for real. After all, swallows have been here nearly seven weeks now, and pairs began forming six weeks ago, but aside from a few bits of dead grasses there’s nothing in any of the eight boxes remotely resembling a nest. So, to see if my impatience was justified, I decided to review this grid’s records from the past nine years to determine if nest building truly is abnormally late this year.
First, let me explain how I define the start of nest building. As we’ve seen, female Tree Swallows often bring a few bits of vegetation into their nest cavities early in the season. These are often termed “claim grasses”, but if they are meant to claim a cavity the claim certainly isn’t honored by other swallows. A pair must often spend weeks repelling other Tree Swallows who would like to kick the original owners out, claim grass or no claim grass. Personally, I believe these early bits of vegetation signal a brief post-migration transition into the nesting season, a slight tweaking in the female’s hormonal balance, nothing more. The shift to true nest building comes several to many weeks after arrival when, like a motor that sputters and sputters before it finally catches, the females rather suddenly start bringing large amounts of vegetation into their boxes. It really is as though an internal switch has been thrown.
When, in checking boxes, I find a substantial ring of vegetation around the outside of a box’s floor, a ring that wasn’t there the previous day, I label that day the start of “real” nest building in that box. And when the female has covered the box bottom with vegetation and formed the cup that will hold her eggs, I note in my records that her nest building is complete as of that date. I do not include feather-gathering by males or females in this formula, since feathers may continue to be added for many more weeks.
So, here’s some statistics. We had 86 nestings at Salmon Creek in the last 9 years. Four of these nestings had takeovers that interrupted nest building, and 16 were late nestings in boxes added in May to reduce competition. But of the remaining 66 nestings where nest building began “normally”, 50 of them, or 76%, began during the eleven-day period between 4/29 and 5/9. In other words, this year could still easily fall in the normal range if most of our females begin to build in the next ten days.
Actually, there were some encouraging hints today that nest building is about to start in earnest. As I sat with the swallows at Box 2 the female began gathering dried grasses and other vegetation from the ground, and she went right into high gear, bringing piece after piece into the box. As I watched for the half hour she stopped only to help the male ward off floaters or to dash away in response to raptor alarms. Box checks later revealed some additions of vegetation in Boxes 1 and 3 since yesterday also. I think the female Tree Swallows of Salmon Creek are on the verge of an intense bout of nest building and, if so, they’ll be right on time after all.
Post 33, April 30
A Takeover Attempt At Box 7
The field was remarkably quiet when I walked in this morning. It has tended to be less noisy in general recently – the cold spell seems to have reduced the number of birds bickering over boxes. Many of the Tree Swallows present today were away from the boxes, foraging high in the air for windblown insects or hunting low over a small pond near the hedgerow. There seemed to be almost no floater intrusions occurring, but appearances turned out to be deceptive.
Shortly after relaxing into my chair by Box 2 I noticed a commotion across the way at Box 7. Swallows were milling about the box, screaming non-stop. I watched two birds fly at each other repeatedly, then fall to the ground locked together, where they continued to flail away. Finally they separated, and two of the assembled group flew to the box while two others perched on plant stems nearby. (I’ve been noticing lately that some floaters, like the two sets below, act paired, even though they don’t possess a box).
Thinking things had settled down at Box 7, I returned my attention to the females I’d seen bringing vegetation to Boxes 1 and 3 earlier. But from time to time I couldn’t help noticing fresh combat at Box 7. One or more of the floaters was being very persistent today, as Tree Swallows without nest cavities tend to become as the season advances.
The situation seemed to have calmed down once again by the time I made my round of box checks, but as I stood on the dry-wall bucket that serves as my stool, preparing to open the door to Box 7, I heard muffled thumping inside. Knowing from experience what to expect I quietly eased the door open and gently grasped the two swallows which were grappling on the box floor. It isn’t uncommon for fights begun outside to continue inside boxes, or for one swallow to discover another in its box and attack it there. The urge for floaters to take over a nest cavity is becoming very strong now, and contests, severe contests, can last on and off for days until one swallow is victorious and the other driven off, or even killed.
Before I released these two fighters I checked for injuries – none found. I also felt their chests to evaluate their flight muscle condition. The Pectoralis majors weren’t as full as they could be but the birds didn’t feel emaciated either, thank goodness. They’d need to be in pretty decent shape to fight the way they had been. I wish these two could settle their differences peaceably, but understand it isn’t likely. Perhaps I should put up some extra boxes sooner than planned.
Here’s a video showing just how serious fights inside boxes can be:
Post 34, May 2
The Bobolinks Are Back And The Swallows Are Building At Last
I’m sure you know the feeling, that one you get when you enter a familiar place, sense something’s a bit different, but can’t quite put your finger on what it is. That’s how I felt this morning as I passed through the hedgerow into the grid field. There was a presence, something that wasn’t there yesterday – what the heck was it? And then, suddenly, hearing a bubbly, gurgling song rising from grasses, I knew – the Bobolinks were back!
Bobolinks have a special significance for me, for they, more than any of the other birds I see here, demonstrate vividly that we live in one world whose far-flung parts are interconnected in unexpected ways. For the Bobolinks I saw this morning had journeyed all the way from Argentina, Bolivia, or Paraguay to nest in this insignificant field in upstate NY. Each year I welcome these long-distance migrants back, for their songs will form a major part of the background music as I watch the swallows. And speaking of the swallows, they’ve finally begun building.
Three of the Tree Swallow boxes now have partial nests, similar to the one above, with coarse dead field grasses from last year arranged in a ring around the outer floor of the box. And you’ll notice they are concentrated on the side below the entrance hole. (You can distinguish the entrance side by the horizontal cleat that is positioned below the hole). It’s very typical for female Tree Swallows to build their nests so the cup that will hold their eggs and small nestlings is located along the back wall or in one of the back corners. We don’t really understand why they don’t center the cups the way many other species do. Perhaps they instinctively want the cups as far from the entrance, and thus from the reaching arms or beaks of predators, as possible.
I probably should have qualified things when I said the swallows were building. Only some of the females are building; those in Boxes 1, 2, and 3, all located in the east row of boxes, are. And Box 4, which had been the last box with no grasses at all, today had two. I know, it’s not much but it signals a change in the female’s behavior. The other four boxes, over in the west row, all have a few grasses but their status hasn’t changed in weeks. Why they aren’t progressing I have no idea, but the lonely piece of curly grass in Box 6 that I’ve seen on every check since 4/6 sure looks like it could use some company. Come on you western ladies, time to get busy.
Post 35, May 4
So, What Are The Males Doing While The Females Build?
In spite of almost daily rain here most of the female Tree Swallows possessing boxes continue to gather nest material. Box 3, above, has reached what I call the 1/2 cup stage, with a substantial ring of grasses around the outside of the box bottom but quite a bit of bare floor still showing. Boxes 1 and 2 females are adding to their 1/4 cup nests, but at a rather slow rate. Box 4 seems to have stalled temporarily, but the Box 8 female has finally begun. Reading this, I wouldn’t blame you if you wondered if all the responsibilities seem to be falling on the females right now. Don’t the males share in the work?
Although they’re not doing the building, male Tree Swallows do have a role during nest building. It’s pretty much the same one they’ve been playing since they first claimed their boxes – using calls, physical displays, and chases to defend their box against intruders – and here at Salmon Creek there certainly is an abundance of intruding floaters this spring.
A male that successfully prevents floaters from interrupting makes it easier for a female to devote her time and energy to gathering nest material. I think it’s no coincidence that at the Salmon Creek grid this year the boxes where nest building has lagged, Boxes 5, 6, and 7, are the same boxes where floaters are concentrating their takeover efforts. Along the east row, box defense and nest building, have both been more effective.
Males also act as though they are genuinely “interested” in the females’ nest building activities. A male will often give a soft, gurgling “contact call” as the female returns with vegetation, and he may peek in the entrance and gurgle to her as she arranges things inside. It’s been suggested that this helps cement the “pair bond” between the two, and may “encourage” the female to keep up the good work, or at least to keep working. Sounds like a male thing to do.
To hear a YouTube video of this call click here:
Sometimes though, it does seem the males are just in the way.
But lest you think male Tree Swallows don’t contribute anything to the nest building effort, we should mention that males are the primary gatherers of an important nest component, feathers. And the first nest feathers in the grid boxes appeared way back on 4/28, most likely brought in by the Box 1 male. We’ll have much more to say about feathering Tree Swallow nests in days to come.
Post 36, May 5
The Migration Event Of The Week Wasn’t Birds, It Was Butterflies!
Well, a few hard-core birders I know might debate the above statement. After all, a nice push of neo-tropical bird migrants arrived here this week; a good variety of warblers, vireos, orioles, flycatchers, etc. But the weather systems that brought these birds in probably also brought the week’s really noteworthy migrants, an absolutely huge influx of Red Admiral butterflies!
One local naturalist, a former hawk watcher highly skilled at counting fast-moving objects, estimated Red Admirals dashed past him at a rate of 200 butterflies per minute during a 15-minute burst of warm winds! The staggering number of Red Admirals that blanketed the Rochester area on 5/3, the peak day, was noted by so many people that it made the TV and newspapers. Of course, it would be impossible to measure, but if someone told me this flight of butterflies numbered in the tens of millions locally, I wouldn’t argue. I, personally, have never experienced anything like it. And reports of this mass irruption aren’t limited to upstate NY; they’re coming from all across the northeast and mid-western US and eastern Canada as well! We’re probably talking hundreds of millions, or even billions of butterflies!
Where did they come from, all these beautiful orange, brown, black and white butterflies? I checked a few sources and found that migratory tendencies of Red Admirals are well-known. They over-winter as adults, but primarily in the southern US down through Mexico. The ones we’ve been seeing are either last year’s adults that migrated all the way north this spring, or ones born along the migration route this year. The species’ larvae feed primarily on nettles, and the adults fuel up on tree sap and flower nectar. Various interacting factors, especially seasonal weather and food availability, can cause major cyclical rises and falls in Red Admiral numbers from year to year. Seems the population exploded this year! Is it due to the record warmth along the migration route perhaps?
I can attest that Red Admirals fly very fast. They darted and zigzagged so rapidly that I had an impossible time getting any photos. Then finally, in the late afternoon of 5/3 I found a group sunning themselves on the trunks of my backyard oak trees and in my vinca groundcover, which allowed me to get off a few decent shots. These individuals actually appeared a bit worn. I wonder how far they’d already come?
Today, 5/5, there are still a few Red Admirals around my yard, but a strong, cold north wind may be pushing the majority of the regional migration flight farther inland from the Lake Ontario shore. Oh well, it was certainly fantastic while it lasted.
Post 37, May 6
Tree Swallows As Individuals: Meet “The Big Guy”
Each year, as I make daily visits to the box grid, I begin to notice individual differences in some of the Tree Swallows. I think we all have the tendency, at least at first, to lump animals and plants by species. “Oh, there’s a Bur Oak”, or “There’s a Cardinal”. But they are all individuals, each with a unique variation of their species’ genetic code, and each with its own unique set of life history experiences. Think how we recognize those people who are familiar to us. Our knowledge of their unique and complex set of physical aspects and behavioral patterns allows us to separate them from all other people in our minds. We recognize them instantly, without conscious thought. We must have an innate mental search method of some sort that scans the variables each person presents to us and allows us to make recognitions.
The Big Guy is one individual I recognize, and he’s an old friend. Two things about him stand out. Although many males are slightly larger than females, Big Guy is the biggest Tree Swallow I’ve seen of either sex. And he’s either extraordinarily tame or extremely trusting of me, for he often permits me to approach within three feet before he takes off.
I first “met” the Big Guy five years ago, when I was putting up a couple of late boxes to reduce competition by giving some of the floaters a chance to nest. I had put the box, pole and tools on the ground, and was trying to decide where to dig the hole for the pole when out of the corner of my eye I noticed something. A swallow, a large male swallow, had landed on the box and was inspecting it, almost at my feet. Carefully, I reached for the camera. He remained perched on the box and peeked in the hole, completely oblivious to me snapping photos of him as fast as I could from only a few feet away.
I suspect Big Guy was a second-year bird back then because he had been floating. He may not have been able to secure a box because he had arrived late with the other second-year swallows and wasn’t skilled enough yet to take a box away from a more experienced male. However, he certainly grabbed this late box fast, and almost immediately attracted a SY female floater. She laid six eggs and together they fledged five young. My records don’t show where he nested the next year, but in his third and fourth years at the grid he claimed Box 8 and nested successfully, and he’s back there again this year, unmistakable, big and bold as ever. Nice to have you back old friend!
Post 38, May 8
Here’s A Nest Building Progress Report
I’d hoped to have some really nice new shots of female Tree Swallows bringing vegetation for their nests, but the weather hasn’t cooperated and I haven’t been sitting at the right box at the right time. So, the photo above is from a previous year, but you get the idea.
Nest building is moving along now at all eight Salmon Creek boxes, but as expected not every nest is at the same stage of construction. This is partly due to individual differences among the females. But it also reflects varying degrees of interference from floaters at the different boxes, for resident females must drop their nest building temporarily if rival females intrude, intent on taking their boxes. Resident males may drive off intruding females, but this can’t be counted on, so to be sure resident females must dash back to chase off other females. And if there is a persistent female floater around a box, the resident female doesn’t get much work done.
Here’s a series of shots showing how the nest in Box 2 has been built.
If you would like to see just how a female constructs her nest check this in-box video from Francois Paquette of Quebec. It’s cool!
The Box 2 female must have been really busy between 5/5 and 5/7. Notice how on 5/7 the vegetation has been piled up almost to the lower cleat. Notice also how, in true Tree Swallow fashion, the cup is closer to the back of the box than the front. The cup, rather undefined right now, will become more obvious as the female continues to shape it with her body in days to come. Box 3 is also at the complete cup stage, with Boxes 1 and 4 close behind at 3/4 cup. Boxes 5-8 are building but lagging somewhat. The situation at Box 8, Big Guy’s box, is interesting. Last year it contained the first nest completed, but it was the last in volume yesterday. Since there has n’t been much floater activity around Box 8 this year, it makes me think Big Guy has a new mate. Last year’s female may have died, she may be at another Salmon Creek box, or she may have been demoted to floater.
My records for the past nine years show that there is usually a delay between the time a nest reaches the complete cup stage and the appearance of the first egg. The interval ranges from roughly 4 to 12 days, with an average of 7 to 8 days, and probably allows Tree Swallow females to recuperate a bit after the exertions of nest construction, and to feed heavily, building up the resources their bodies will need for ripening and laying eggs. And before the eggs are laid the swallows have to – – -, well, you know.
Post 39, May 10
Yes, Birds Do It, And Tree Swallows Do It A Lot!
Two mornings ago, 5/7, as I was getting ready to leave the grid after making box checks, I heard a series of tell-tale “tic-tic-tic” calls that told me some Tree Swallows were “getting it on” I turned around just in time to snap off a couple of shots. The pictures turned out to be poor quality but I think you can tell what’s going on.
I’ve been expecting mating behavior from those pairs in which the females are nearing the end of the plant material gathering stage of nest building. Eggs should be appearing in the boxes within the next week to ten days or so, but before each egg is laid sperm from a male must fertilize the unshelled egg inside the female swallow’s body. So, the interval from now until the end of egg laying is when most Tree Swallow copulation will be taking place.
Copulation in birds always seems like an awkward process, but judging from the number of birds around it does appear to work. If you haven’t seen Tree Swallows in action before you can watch the short video below I took yesterday, 5/8. It’s a very typical sequence in which the male lands repeatedly on the female’s horizontal back, and balances as best he can by gripping her head feathers in his bill and spreading his wings. You should be able to see him pivot his tail under the female’s in order to make cloacal contact. Sperm is transferred from the male’s CP, its “cloacal protuberance” (songbird males don’t have penises) to the female’s vent with each contact.
I also recommend you check the still photos of tree swallows mating, some taken by real photographers, on the web page below. Among other things the page shows a male’s breeding season cloacal protruberance and a female’s vent, both difficult to observe in wild songbirds.
I expect to witness many Tree Swallow copulations during the next two weeks or so, because when these birds begin to mate they mate a lot! Canadian researchers studying Tree Swallow reproduction found that this species averages over 50 successful copulations per pair! This is significantly more than for most other songbirds. And since most Tree Swallow copulations involve multiple cloacal contacts, the total number of contacts must number several hundred per bird. But since each female really only needs enough sperm to fertilize 5-7 eggs, you may well ask yourself what’s going on here? Isn’t all this mating just a bit excessive? Since this is an important and interesting question we’ll return to it in a later post.
Post 40, May 11
Some Boxes For The Floaters And Some Relief For The Residents
I’ve referred many times on this blog to the competition between those Tree Swallows who possess boxes and those who don’t. Each year some swallows without boxes hang around the grid, approaching boxes and testing the resistance of the residents to their intrusions. The primary goal of these “floating” birds, of course, is to obtain a nest site for themselves, either by detecting a weakness in a resident indicating it can be driven out, or by discovering a vacancy caused by a resident’s death or desertion. Every year it’s the same story, more birds than boxes, proof positive that for tree swallows here there is a chronic shortage of suitable nest sites. My response to the floater situation for the last six years has been to add 2-4 more boxes in May. Why May? First, because I want to let the strongest birds become fully established as residents with boxes, building nests and laying eggs. Second, I want to get a firm estimate of how many floaters remain in the area and need to be accommodated.
However, this year I decided not to wait for egg laying to begin to add boxes. The residents really need a break from floater intrusions so they can concentrate on more important things like finishing their nests and stocking up nutrients required for the next stages of the breeding cycle. And perhaps I was just getting impatient but I felt the floaters who’ve lingered loyally at the grid deserved their own chance to begin reproducing now too. After all, missing a breeding season is a big deal for a Tree Swallow whose average life expectancy is estimated to be less than three years. So, yesterday, 5/10, my son and I added Boxes 9, 10, 11 and 12 to the grid.
The response was immediate and dramatic. Swallows converged on the boxes from all directions, milling about and calling excitedly.
I’ll have to wait now and see how fast the ownership of these new boxes is decided, and if four will be enough. I’m also curious to learn how many are successfully claimed by second-year (brown) females – there are at least two among the floating group. One thing I’m already certain of though is that the original eight pairs of residents won’t miss the strife and turmoil the former floaters caused. The new boxes will be a cause of relief for them.
Post 41, May 13
The Floaters, Now Residents, Catch Up (With Some Help)
It’s pretty amazing. It took the Tree Swallows of Boxes 1-8 well over a month from the time they claimed boxes and established pairs to the point they really began nest building, and then another 4-12 days for their nests to reach the “complete cup” stage. And Boxes 7 and 8 still aren’t there yet! However, the floaters, now residents, who have occupied Boxes 9-12 are a different story. These four boxes, put up 5/10, were claimed almost immediately. Pairs seemed to form within minutes (although it’s possible some of the floaters were at least “associated” beforehand), and nest building commenced within hours. In the photos below you can check the progress the female in Box 11 made in a very short time, and the status of this box is typical of the other three new boxes.
However, I have a confession to make – I helped. For the past few weeks I’ve watched the original eight females build. In typical Tree Swallow fashion, they would fly out from their boxes, slowly circle around, dip down for a closer look, and continue this process until they spotted suitable dried grasses or other field vegetation. Once found, the swallow would try to land, wrestle the vegetation free, and return it to her box. But this year it seemed to take them an unusually long time to locate material to their liking. Several factors could be involved. The warm early spring here got new plant growth off to a fast start, covering up the old stuff the swallows preferred. And the field wasn’t mowed last summer, meaning there were many broken weed stems pointing up, hindering landing by the female swallows. Long story short, it appeared to be significantly harder than normal for the females to find and gather plant material for their nests this year.
Now if it had been difficult for the original eight females to find and gather nest material, how much more so would it be for the four former floater females now in Boxes 9-12, who were starting so much later, after the field plants had already shot up considerably? Perhaps there was something I could do to assist. As an experiment, on the morning of 5/11 I pulled up a couple buckets worth of dead grasses and spread handfuls loosely under each of the four new boxes, and also under Boxes 5-8 which didn’t hold complete cups yet. Would they use it?
Did they ever! The four new resident females went right to town gathering the grasses offered. One day later, 5/12, Box 10 had reached the 1/2 cup stage, and Boxes 9, 11 and 12 were already 3/4 cups. Boxes 5 and 6 went from 3/4 to complete cups, and Boxes 7 and 8 were close behind. And this morning, 5/13, Boxes 9 and 12 had complete cups and Boxes 10 and 11 were almost there.
Is there a lesson here? One might be that the floater females didn’t have to go through a long period waiting for their internal systems to reach a threshold for nest building. The necessary internal metabolic changes had already taken place, and they were ready and willing to start nest building immediately – all they lacked was a nest site, and the minute they had one it was full speed ahead!
However, before I close for today here is one more twist – the female you saw on the Box 11 crossbar in the photo at the top of this post is not the female who built the nest shown in the box. Today, 5/13, as I approached this box I heard and then saw a big fight going on. The photo above was taken when I returned several hours later, after the battle’s conclusion. A takeover had taken place, and this takeover will be the subject of the next blog post.
Post 42, May 14
Female Versus Female: A Takeover At Box 11
Four new boxes weren’t enough. As I approached Box 11 early yesterday morning, 5/13, it was clear there was a serious fight in progress. Two Tree Swallows were grappling in the air, and as I watched they tumbled to the ground locked together. I hurried up, camera in hand, and quickly fired off several shots before they realized I was there. Then, becoming aware of me they separated, and one, an older, after-second-year (ASY) female with bluish upper body plumage, tried to fly to the box. But she was quickly overtaken by the other swallow, a brownish second-year (SY) female, who attacked, driving the ASY bird to the ground again. They separated once more when I approached, and this time the ASY female made it to the box and ducked inside, but the SY female was right behind, pursuing her in.
Two days ago, on 5/12, Box 11 had been in the possession of an ASY female, presumably the one here today, and she had been gathering plant material for her nest in routine fashion. But today, she was a beaten and exhausted bird, her nest site being taken away by a younger and apparently stronger rival. I felt I had to intervene because if she was cornered inside the box this ASY female could be seriously injured or killed. I opened the box, removed both birds, released the SY female and walked a good distance away with the ASY female. She had no obvious external damage but this didn’t mean she was unharmed, so I continued several hundred feet toward the hedgerow before releasing her. She flew weakly east out of sight. I hoped for her sake she wouldn’t return, at least not until I had a chance to add one more box.
As quickly as I could I went home, assembled my gear, then brought another box back to the field and raised it 120 feet from Box 11. This time there was no crowd of floaters to examine it – most former floaters are now full-time residents. If the defeated ASY female does return, Box 13 will be available for her, unless there is another, stronger female out there waiting for a nest site.
Are you surprised that the most intense fighting at Salmon Creek is between females? Think about it – female Tree Swallows cannot reproduce unless they have a nest cavity to lay their eggs in, and there is nothing more important in their lives than reproducing.
On the other hand, male Tree Swallows can reproduce without a nest cavity – all a male has to do is find a female with a nest site that’s willing to mate with him, and he has a chance to father young, young another male will end up raising. And as it turns out many female Tree Swallows are willing.
Post 43, May 15
A Box 13 Update, And Something Else
Yesterday morning, 5/14, I was eager to learn if the blue-backed after-second-year (ASY) female that had been ousted from Box 11 had moved over to the newest box, Box 13, but she hadn’t. Instead, a brown-backed second-year (SY) female was there, in very complete possession.
This female was in full box-claiming mode. She wouldn’t allow any other Tree Swallow, female or male, at the box, launching herself at any that tried to approach. She was strictly on guard, with no courtship behavior that I could discern, and although she peeked in repeatedly, I didn’t observe her enter the box. When I checked the box it was completely empty.
However, today, 5/15, was a different story altogether. As soon as I passed through the hedgerow I could see two swallows at Box 13, and as I came near it was clear a pair had formed. The SY female was busily gathering dead grasses I’d left under the box and carrying it through the entrance, while the male perched on the bar calling to her with his soft sweet gurgle – the very picture of Tree Swallow domesticity. And when I checked the box later it already contained a nice 1/2 cup nest.
The ASY female that had been defeated in the Box 11 takeover was nowhere to be seen. She lost several flight feathers in the fight, and I’m pretty certain I would have noticed her had she been present today. I wish her well, wherever she is, but I doubt she’ll nest this year.
And the “Something Else” I mentioned in the title of this post? Today Box 4 held the first Tree Swallow egg of the Salmon Creek 2012 nesting season. Laying has begun.
Post 44, May 17
A Quiet Tree Swallow Grid? Really?
What a difference a few days make! Today, 5/17, as I sat in the middle of the 13 box Salmon Creek grid, now home to 26 adult resident Tree Swallows, I could close my eyes and sometimes not hear a single swallow unless I concentrated hard. I know, it’s tough to believe. But the non-stop chattering racket of box claiming is over now, and since most or all the floating population have been provided with new boxes, there is little cause for nest defense screams. Plus, it would actually have been difficult for even a bit of swallow song, or a gurgle or two, to make itself heard over the raucous din from all the male Bobolinks displaying.
It does seem that the appearance of eggs often ushers in a period of relative calm, at least to my human eyes. Sure, boxes may need some token defense if another swallow happens to pass too close, but it’s common now for one or both members of a pair to leave the box on extended foraging trips. After all, females need as much nourishment as they can get at this time. They’ve already put in a lot of tough hours building nests and now they have four to seven eggs to produce, one per day, and those eggs may be little but they’re “expensive” in terms of materials needed. After all, these swallows aren’t that big themselves, and each egg a female Tree Swallow lays weighs almost one tenth of her own body weight.
As for the males, well I don’t think they have it so hard, but their testes do have to enlarge greatly in order to manufacture all that sperm they’d like to donate at this time, and I guess this metabolic change probably requires extra food intake.
Before I close this post here’s an egg-laying update. Yesterday, 5/16, first eggs appeared in Boxes 1, 2 and 3, and today the females in Boxes 5 and 9 laid their first. And since every box in the grid has completed the vegetation gathering stage of nest building, even Box 13, the other females should start laying soon. It looks as though reproduction will be very synchronized this year.
There’s more on eggs and egg laying on this web page:
Post 45, May 18
What The Swallow Nests Tell About An Invasive Species
The Tree Swallow nests at Salmon Creek are telling a story. They are evidence that wildlife management officials have been forced to use techniques of last resort in order to contain and reduce the damage caused by an invasive species. Compare the nest material in the two photos below. Pretty obvious difference, isn’t there.
Actually, the first nest is very typical of most years here, and reflects the strong preference of Tree Swallows for white feathers to line their nests. These swallows, especially the males, will fly long distances in search of the white feathers they prefer and on their return they are often chased by other swallows hoping to steal the feather.
Although both males and females bring feathers into the boxes, it’s the females that do the arranging. You’re not surprised are you? You can see this process in the next video.
However, at Salmon Creek this year white feathers appear to have been hard to find so far. With few exceptions nest feathers this year are dark, coming primarily from Canada Geese, Wood Ducks and Mallards, instead of their main source of the past nine years, the white-feathered Mute Swan.
The Mute Swan is a very large, non-native, invasive species. Brought to North America from Europe for private ornamental waterfowl collections that were once popular, some swans were deliberately released and some escaped, and found conditions to their liking. Gradually their numbers built up to tens of thousands of wild-living birds, especially along the East Coast, and eventually complaints arose that they were driving out or killing native waterbirds and destroying large areas of submerged aquatic vegetation needed by many other species of wildlife. Along the Lake Ontario shore of New York where I live the increase of Mute Swans since their arrival here shortly before the turn of the century is widely believed to be related to the local loss of several native waterbird species, including one of my favorites, the Black Tern.
To many people Mute Swans are the epitome of beauty, elegance and grace, and no one could deny they are gorgeous birds. But the consensus among most government wildlife agencies and private conservation groups is that Mute Swans have had a major detrimental effect on native ecosystems wherever they’ve established themselves in numbers in the New World. And so, despite some strong popular sentiment, Mute Swans are now being “controlled” in many areas.
Mute Swan control takes several forms. Eggs can be coated with vegetable oil or shaken, both actions destroying the embryo. But Mute Swans have long life spans, so a pairs’ eggs would have to be located and treated annually for many years to really limit the species’ increase. Killing the adults is far more effective, and this is now being done in many areas, including, given the evidence of the swallow nests, the Braddock Bay Fish and Wildlife Management Area of NY. When it became clear during the past week that the Tree Swallows of Salmon Creek weren’t finding many swan feathers I made a quick car search for Mute Swan nests in the local ponds, creeks and bays. I’ve done this in other years, usually locating 10-15 nests or broods with no trouble. This week I found one brood in a quiet backwater, with another possible at the far side of a pond, no more, although there may have been others in more remote spots. And the total number of adult swans I counted was well below what I’d come to expect. It’s rather obvious to me that elimination of adults has become the technique of choice here this year.
I think this tale illustrates the often difficult actions wildlife management personnel must perform in order to protect and steward our native ecosystems. I can’t imagine having to take lives to save other lives is pleasant for anyone. But, unfortunately, trying to undo human mistakes, such as the introduction, accidental or deliberate, of destructive non-native species is all too often part of their job.
Post 46, May 21
More And More Eggs Every Day
I’ve had to stop going to the grid field early because most female Tree Swallows are laying eggs now and, since egg laying usually occurs in the hour or two after dawn, I don’t want to disturb them in the act. Laying an egg appears to me to be a strenuous task, at least it appears so in the video below from Kathryn Leonardo. Since I’d rather be on the cautious side I stay away until after 9:00 AM. But I do miss the crisp air and the vivid light of the earlier hours, and I do get impatient to see how many more eggs have been laid since last check.
Well, here at Salmon Creek there are eggs aplenty now. The count has climbed from one lonely little white Tree Swallow egg on 5/15 to 54 eggs this morning, 5/21, and all thirteen nest boxes now contain eggs. And it was only five days from the first laying start in Box 4 to the last laying start in Box 13 on 5/20. The female swallows are extremely synchronized this year, I think because they were probably all present for several weeks and together experienced the period of prolonged severe weather that acted to set every one’s hormonal clock to the same approximate time.
I’m really curious whether the swallows’ very early spring arrival and their consequent need to endure a longer than normal period of pre-laying cold might affect the egg production of these females. We’ve had a very nice stretch of weather recently, but will this offset the hardships their bodies endured earlier, when for weeks the foraging was difficult? My guess is no. I suspect the poor weather has had lingering detrimental effects on the female swallows’ physical condition. Females here usually lay between five and seven eggs, but I expect that there will be few if any seven egg clutches this year, which I would interpret as a sign the living has not been so easy. I also think the average clutch size this year will be below the nine-year average of 5.81 eggs per female. We’ll soon see which (if any) of my predictions prove correct.
Back in the post of 5/13 I noted that the females from the former floating population were extremely quick to build nests once I added boxes for them to build in. These females have also been very quick to begin egg laying, and their boxes are now at the same reproductive stage as the eight earlier boxes for all practical purposes. While the original eight resident females took an average of 6.4 days between the time their nests reached the complete cup stage and the day on which they laid their first egg, the five females in the boxes added later only took 3.4 days on average. This shows once again that these former floaters were ready, willing and able to nest. Their internal clocks were already set and their metabolisms geared up, just waiting for the right stimulus to trigger the necessary Tree Swallow breeding behaviors. The only thing they lacked was nest cavities.
And although the vegetation gathering phase of nest building is over, the search for feathers continues. A few small swan feathers are starting to appear in boxes, and somewhere in the neighborhood there must be a decomposing hen Mallard carcass, because many of her body feathers are finding their way into Tree Swallow nests. Her loss is the swallows’ gain.
Before I close there are two things to report from Box 4, one unexpected and sad, the other an anticipated milestone. First the sad: Upon opening Box 4 today I found a dead SY female Tree Swallow. She was emaciated, which surprised me because the foraging conditions have been excellent for more than a week. But after closer examination I suspect she sustained an eye injury, probably battling for a nest site, and if so, it may have hampered her ability to catch flying insects, until she sought a final shelter in Box 4 and died.
The second news from Box 4 is that the resident female there, an older ASY bird, has stopped laying, the first female at the grid to do so. Her clutch is six eggs, and they were warm to the touch. The next stage in her reproductive cycle, incubation, has begun.
Post 47, May 23
The Heat Is On: Incubation At The Grid
As of this morning, 5/23, six female Tree Swallows at Salmon Creek have finished egg laying and have begun incubating, which is another of those reproductive tasks that in Tree Swallows is done only by females.
On the surface things may seem a bit boring now, at least for us humans, but looks can be deceiving. Until incubation starts with the laying of the last or next to last egg, no growth has occurred inside the eggs. But now, with the application of heat from the females’ bodies, the processes of embryonic development from one-celled fertilized egg to complex organism have suddenly been kicked into high gear. Tremendous changes are occurring, changes that are much more dramatic than those we will see nestlings undergo between hatching and fledging. Within these incubated eggs embryonic cells are dividing, migrating about, and differentiating into tissues, organs, and organ systems at a furious rate under the coordination of chemical gradients established by master “selector genes”. It’s a shame we can’t see inside and witness these developmental changes because I think we’d be truly awed. You can peek inside a developing swallow egg in this video:
So just how does a female Tree Swallow “turn on the heat” of incubation? By the end of egg laying she has lost most of the feathers from her breast and abdomen, and the bare skin of this region thickens and becomes engorged with blood vessels. When the female presses this “brood patch” (BP) on her eggs, heat carried by her blood passes to the eggs, raising their internal temperature to the point that the chemical reactions necessary for embryonic growth can proceed.
For me incubation sometimes presents one minor inconvenience. Incubating females are very reluctant to leave their eggs, so when I make box checks and find an incubating female inside I gently close the door, back away, and wait for her to leave. However, the problem is she might not budge for 10-15 minutes, and if this happens at several boxes in a morning, it makes for a long round of checks. I don’t really mind waiting though – it’s an opportunity to sit down on my bucket/stool and watch what’s happening around the rest of the field. I never get bored here.
For more on incubation see this web page:
and for in-box female incubation behavior check this video from Francois Paquette:
Post 48, May 24
Control Sheets: Grid Nest Status At A Glance
As I hope you’ve seen Tree Swallows are remarkably tolerant of human presence. However, now that incubation is in full swing it’s probably best not to push our luck and disturb incubating females unnecessarily. Up to this point I’ve been checking every box daily, but during both incubation and the first 12 days of the nestling period I’m going to reduce box checks to every third day. The problem is how to remember which boxes to visit on any given day. The solution is to use a Control Sheet.
Control Sheets are an organizational device that lets you see at a glance the status of every swallow nest and that records important facts and milestones regarding each one. Control Sheets also permit you to schedule box checks systematically, in order to prevent excessive disturbance. In addition, Control Sheets can suggest the proper dates for trapping and banding adult swallows and identify the crucial short window for banding nestlings. Plus, Control Sheets tell you exactly when to stop checking boxes altogether to cut the risk nestlings will fledge prematurely. Long story short – Control Sheets can be extremely useful for anyone monitoring Tree Swallow nests.
Let’s get familiar with Control Sheets by taking a quick peek at one of today’s.
Starting from the left, the first three columns list Box #, First Egg Date, and Last Egg Date. Next is Clutch #, which is the total number of eggs the female laid on this nesting attempt. Then comes Egg #, which is the number of eggs present at the end of incubation, just before hatching; this could be less than clutch # if eggs have disappeared or been broken.
The next four columns list dates during incubation when the box should be checked (Last Egg Plus). You should see they are at three-day intervals, counting from the date the last egg was laid. After a box is checked on its appointed date a red line will be drawn through that date on the sheet.
Moving along in the nesting cycle, and farther to the right on the Control Sheet, Hatch Date is the date the majority of eggs in the clutch hatched. Brood # equals the number of young known to hatch, which may be less than the Clutch # and Egg # due to embryo mortality or egg infertility.
Hatch Day Plus lists three-day intervals for checking status of nestlings. The best time for banding adult swallows is between hatch and day 6. Nestlings should be banded at day 11 or 12, and box checks should stop at day 12.
Brood # D 12 is the number of nestlings surviving at that date, and Fledge # is the day 12 brood number minus the number of dead, if any, found in the box after fledging. No checks are made between Brood Day 12 and normal fledging to reduce the risk young swallows will jump from the nest before they can fly well.
I can’t emphasize enough how very handy it is to have a system like this to structure one’s management of a multi-box grid, and once again I’m indebted to the late Dr. David Hussell of the Canadian Ministry of Natural Resources and the Long Point Bird Observatory for its development and for exposing me to its use.
Post 49, May 26
Homemade Predator Guards: Protection On The Cheap
We’ve finally reached the stage when almost all the female Tree Swallows at Salmon Creek have finished egg laying and are now incubating. But when incubating they must spend the nights in their boxes in order to maintain the necessary passage of heat to the eggs. This puts these females in danger from mammalian predators like cats, opossums, and especially from raccoons, so the onset of incubation is the time I mount predator guards on my poles. Since my predator guards have edges that could injure a swallow that flew into or was driven into one, I prefer to keep the guards off during the more strife-filled box claiming and nest building periods. But now they go on.
One of the most disturbing things that can happen to anyone who puts out nest boxes for birds is to find them predated, with eggs, young and/or adults killed or vanished. In my opinion careful box placement will prevent most predation, but I prefer to go it one further and equip each of my boxes with predator guards. The trouble for most people, me included, is that commercial guards are prohibitively expensive, especially if you need a lot. But after raccoons cleaned out most of the boxes at another grid one night years ago I was determined to find a way to guard boxes without going broke. After some experimentation here’s the cheap system I came up with.
I remove the ends from large juice cans and cut 6-7 strips to within 2″ of one end of the can. One cut goes all the way through so the guard can be fitted around a pole. Then the strips are bent so they point outward. I wear work gloves when cutting the cans.
I stack three of these can guards on each pole using a simple support of heavy-gauge hanger straps held in place by a hose clamp.
The three can guards sit unattached on top of the support. The theory is that they will be awkward to get around, and sharp-edged and noisy as well. Plus, to make it even more difficult for climbing predators I put a 2-3 inch band of engine grease just below the guard, which also prevents ants from reaching the nests.
You may wonder why I don’t use some of the other methods you’ve seen for predator protection. Well, I don’t believe the wood-block entrance extenders are effective keeping out the hands and arms of something as dexterous as a raccoon. And I really dislike “Noel” wire guards that project out around entrances – I think they make access to the box unnecessarily hard for birds, especially swallows, which must maneuver awkwardly through them hundreds of times each day to feed hungry nestlings.
You might also suppose that thin diameter poles would be enough to keep most predators from reaching boxes. Wanna bet? Check the photo, below, taken by Texas bluebird expert Keith Krider.
I don’t want to jinx things, but I haven’t had a single nest predated in ten years at Salmon Creek. Whether its box location, or the guard/grease system, or both, I can’t say. But I do feel better knowing each of my swallow nests has all the protection I can give it.
Post 50, May 27
Some Bluebird Boxes Are Miserable Little Death Traps
For the past ten days or so I stopped going to the grid early because I didn’t want to disturb Tree Swallow females in the act of egg laying. This wasn’t so bad because it gave me time to take walks elsewhere in the Braddock Bay Management Area. And on one of these I found the nest box below, put up with the best of intentions by a bluebird hobbyist. The problem with this box is the interior dimensions are extremely cramped. I measured the floor – it was 3.5″ x 4.5″, only 15.75 sq. inches! But in spite of this Tree Swallows were attempting to nest in it.
Years ago, someone, somewhere had the bright idea that House Sparrows, also known as English Sparrows, non-native scourges of our native cavity-nesting birds, would not use small boxes because they like to build large globular nests. Nice try, but wrong! There simply aren’t enough cavities around for all the birds that want to reproduce, so House Sparrows will nest in just about any cavity they can fit into, big or small. And so will Tree Swallows.
For weeks now you’ve heard me describe competition among swallows, floaters hoping for boxes, and takeover fights. For small cavity-nesters like Tree Swallows the drive to possess a nest site is intense, and in order to breed they will attempt to use almost any cavities they can claim, ranging from huge Wood Duck boxes down to tiny decorative boxes never meant for actual bird nesting. The swallows don’t appear to have any “judgment” whatsoever regarding the possible shortcomings of some of the stuff we humans offer. But the consequences of choosing inadequately sized boxes can be deadly for their young, and unfortunately many Tree Swallows are drawn to small, so-called “sparrow deterring” bluebird boxes, which in reality are nothing more than miserable little death traps.
Imagine what your life will be like if you were one of the 5-7 young Tree Swallows that have to live and grow in the box above for three weeks? You can’t leave the box when partially grown to hop around the underbrush being cared for by parents like some birds, like bluebirds, do. No, you’re a Tree Swallow nestling and so will remain in your nest until you’re almost fully grown and feathered, because you must be able to fly strongly and far on your very first flight. In this box if you’re lucky you’ll be a bit stronger and larger than your nest mates, and will be able to clamber on top of them to reach the food your parents bring. But if you are a bit smaller or weaker, you’re in deep trouble. You’ll be trampled and become soiled with feces. You’ll be smothered by your nest mates’ warm bodies during hot spells. You won’t be able to position yourself to reach food your parents bring. You’ll lag behind your stronger siblings in growth and development, and the gap will get larger as the days pass. Your bones and feathers may not develop properly. And neither you nor your nest mates will be able to exercise your wings the way young swallows in spacious nests do before they fledge. You may not even live to fledging, but if you do, has your stunted nestling life hurt your chances for long term survival?
In my opinion the North American Bluebird Society and any of its member clubs or individuals that continue to promote boxes with small interiors show a blatant disregard for the lives of other native songbirds, species every bit as deserving of consideration and conservation as bluebirds.
Do you think I’m overstating my objections to bluebird boxes with small interiors? Look at the next picture and judge for yourself. You’ll see a typical brood of six 12-day-old Tree Swallow nestlings sitting in a floor with dimensions identical to my boxes – 33 sq. inches. To its left is another swallow box floor, somewhat smaller at 25 sq. inches. The bottom two are common bluebird design floors, one 16 sq. inches, the other less than 13 sq. inches! Now imagine stuffing the six swallows into either of the bluebird designs, and forcing them to live and develop there for another 8-12 days if they can?
Do you understand why I’m angry at those bluebird hobbyists, clubs and bird supply stores that continue to advocate and sell small cramped boxes, even though they don’t deter House Sparrows? For yourselves, please use a critical eye when you see how people are managing wildlife. Don’t assume they know what they’re doing. More often than not they don’t. And if you don’t like what you see, speak out.
For more on nest box issues see:
And for a Bluebird versus Tree Swallow “reality check” see:
Post 51, May
There’s A New Girl In Box 2
Can you tell what’s wrong with this picture? It’s of Box 2 on 5/23, when I expected to see at least four eggs. Oh they’re still there; but they’ve been covered over.
I guess I should have realized something was up in Box 2 after the first egg was laid on 5/16 but there were no new eggs on either of the next two days, 5/17 or 5/18. Sure, I’d noticed what I thought were a few casual intrusions by other Tree Swallows, but no fights at this box, nothing serious at least during the times I watched. Of course, laying “skips” do occur, usually due to bad weather, but that couldn’t have been the reason; the weather has been outstanding. But apparent laying skips can also be symptoms of takeover attempts, where an intruding female throws out a resident’s eggs or the resident is too harassed to lay. However, when new eggs appeared on 5/19, 5/20, and 5/21 I assumed all was fine at Box 2 after all. Wrong!
On 5/22 I couldn’t ignore the signs anymore. As I watched, a third swallow, a very petite ASY female, flew in and perched quietly with the resident male on the crossbar, while I knew the resident female was in the box. And later when I checked there were only 4 eggs inside, no new one had been laid. A takeover, albeit a rather subtle one, was definitely in progress.
Hoping I could supply this new female with an alternative I put up Box 14, my last Long Point Box, that evening, but by the next morning, 5/23, I found the takeover at Box 2 was complete. The original resident’s four eggs were completely buried under a layer of new vegetation, and while I watched, the resident male repeatedly drove off what I presume was his previous mate.
I really hope this is the last takeover at Salmon Creek this year. Adding boxes had satisfied most of the floating population, and in most boxes eggs have been laid and are being quietly incubated now with no strife worth mentioning. However, there has been a trickle of new birds over the last week or so. While it’s impossible to pinpoint their origin, I suspect they are refugees from a neighborhood home whose owner erected 6-8 closely-spaced boxes in his yard. Some of these boxes are now occupied by House Sparrows, who may have driven out Tree Swallows attempting to nest there.
For record keeping purposes I’m calling this second nesting attempt 2A, and the new little female began laying her own clutch of eggs 5/28. And as for Box 14, a pair of Tree Swallows occupied it on 5/25, where the female built a nest from nothing to complete cup stage in less than 24 hours! Is she the ASY female evicted from Box 2 getting a second chance? I’d like to think so, but I’ll never know. Of course the real losers are the original eggs. They were fertilized but will not be incubated and will not develop. It’s over for them. I’ll find them buried under the new nest when I clean out boxes in July.
Post 52, May 31
Ridiculous Idea #1: Why I Think Second-Year (SY) Female Tree Swallows Are Brown, Not Blue
Please don’t take the opinion I express in this post as fact; it has not been proven, and actually flies in the face of accepted opinion. It’s just an idea I play around with for fun. However, you may find it interesting or thought provoking, because it involves a very odd characteristic of Tree Swallows.
Many bird species have subadult plumages, in which younger individuals look different from older ones. In these species individuals must molt through one or more different plumages as they age before finally attaining their full adult plumage. In quite a few species either both sexes or males only show delayed plumage maturation of this type. However, it’s extremely rare when only females have a subadult plumage, and Tree Swallows are apparently one of only two North American birds in which females only do. Things like this intrigue me – why do Tree Swallows, of all species, have this sequence of plumages? There must be a reason.
The conventional wisdom among respected research ornithologists is that a second-year (SY) female Tree Swallow’s unique brownish plumage signals subordinance, so that other swallows seeing it won’t view her as much of a threat, and won’t attack her as severely if she intrudes, prospecting for nest sites. But I’ve seen way too many aggressive takeovers by SY females to buy the notion that their brown plumage signals subordinance (see below). And I’ve witnessed too many resident females attack intruding SY females on sight to believe ASY (after-second-year) females don’t take the threats of SY females very seriously. So, since I believe this odd situation deserves an odd explanation, here’s my alternative hypothesis.
We know after-second-year (ASY) Tree Swallows migrate north before the younger SY age class, and that the strongest, toughest, “high-quality” birds of this ASY age class claim most available nest sites. When the SY swallows, both males and females, do arrive on the breeding grounds later, they can either risk trying to take a nest site from older more experienced birds or, being unable to out-compete the residents, they can join the weaker, “lower-quality” ASYs and float, prospecting and hoping that a nest site vacancy will occur. A very few, super high-quality SYs might be able to take over early nests, but most SYs will float, and if I were a male Tree Swallow who had claimed a box early in the season, I’d certainly prefer one of the tough older experienced blue ASY females for my mate.
But what if a vacancy for a female occurs later on? Which of the floating females will it go to, a blue ASY female, or one of the brown SYs? If I were a male Tree Swallow with a nest site, “intent” on passing my genes on to future generations, I should prefer to mate with a high-quality female. But how would I distinguish one? Well, at this later time the pool of potential mates includes some blue ASY females and almost all the SY females. By definition the ASY female floaters available at this later tme had not been fit enough to claim and hold a nest site earlier, but among the SY females are the whole range of individuals, from highest to lowest quality in their age class. So, even though an SY female is inexperienced in nesting, she might just be of more superior genetic quality than the ASYs available at this time. And as a male Tree Swallow I can tell the age-classes apart – ASY female floaters are blue, SYs are brown. So, why don’t I let the females fight it out, and if one of the contestants is an SY female that shows any sign of winning, that she’s in fact a superior bird, I’ll throw my support to her.
So there it is – I think the reason SY female Tree Swallows have a unique plumage has to do with seasonal timing and male choice, that early in the season males should support blue ASY females, but when choices have to be made later on it might be better to support brown SY females, or at least not interfere as the females contest the nest site. So, Tree Swallows may present a very rare case where males, not females, are selecting for plumage color differences in the opposite sex. Told you it was a ridiculous idea, didn’t I.
The photo below is from a previous year.
Post 53, June 2
A Visit To The Braddock Bay Bird Observatory
Since it’s been so quiet at the Salmon Creek Tree Swallow nest box grid, with 12 of the 14 females well into their fourteen-day incubation period, I decided to make a side trip to the Braddock Bay Bird Observatory’s Kaiser-Manitou Beach Banding Station. I wanted to say hello to Betsy Brooks, the guiding spirit of the station and my former banding instructor.
Braddock Bay Bird Observatory is a non-profit organization, run by skilled volunteers, and dedicated to ornithological research, education, and the protection of migratory birds and their habitats. The primary banding station is located on the south shore of Lake Ontario, roughly two air miles from my nest box grid at Salmon Creek. The big lake acts as a barrier to migration, and large concentrations of birds often halt here near the shore between migratory flights to rest and refuel, making it an ideal location for trapping and banding.
Banding operations follow a strict protocol to ensure safe and rapid handling of up to several hundred captured birds daily during spring and autumn migrations. The mist nets used for capture are checked frequently and birds are “processed” and released asap. Each bird receives a metal band with a unique identification number. Each is identified by species, and aged and sexed when possible. Several physical measurements are taken, and then the bird is weighed and released. Data is meticulously recorded, first by hand, then into computers, and finally it’s transmitted to the Bird Banding Laboratory in Pautuxent, MD, where it becomes available to researchers worldwide investigating bird migration patterns and geographic ranges, population changes, and identification issues.
In addition to routine banding activities the Observatory collaborates with professional ornithologists and their students, investigating such topics as in-flight calling behavior, migratory orientation systems, and migration stopover ecology. Plus, bander training and certification courses, public demos, and special workshops are all offered at the station. In sum, it’s a pretty neat and dynamic place!
I’m always happy to visit the station – nice people and interesting stuff going on, but I did have an ulterior motive. I have so many swallows this season I needed to get another string of #1 size bands, and I needed them soon because I plan to begin trapping and banding parent Tree Swallows a few days after their eggs hatch. And the incubation period is rapidly drawing to a close at Salmon Creek. I expect hatch to start tomorrow, 6/3, in Box 4, and possibly in Boxes 1 and 3.
Post 54, June 3
Hatching Part 1: The Race Is On
For most of the past two weeks you’d never know 28 Tree Swallows were nesting here at Salmon Creek if it weren’t for all the boxes. About the only swallow calls I’d hear were occasional gurgles as pair members approached and relieved each other. And the swallows haven’t really been all that visible either. Females were either hidden inside their boxes incubating or off hunting food, and males were also away feeding much of the time since they weren’t needed for box defense and the females were no longer soliciting copulations. Males would perch and preen briefly on the bars or peek in the entrances, but that was about it. However, I know from my Control Sheets that the 14-day incubation period is ending or about to end for many nests, and this interlude of relative tranquility is going to change, big time.
Today, 6/3, hatch began, and by 2:00 PM fifteen eggs had hatched in three boxes. In Box 4 all six eggs have hatched, five out of six had hatched in Box 3 and four out of six in Box 1, so far. And this is just the start. Within the next six days a total of between 60 and 70 eggs will have hatched at the grid. That’s 60 to 70 hungry little mouths to feed. Yes indeed, things are going to get busy in a hurry. For these new nestings and their parents the 18-22-day race from hatching to fledging will have started.
During the last few days the baby birds within the eggs in Boxes 1, 3 and 4 had begun to breathe air filtering through the porous eggshells, and they used up most of their eggs’ remaining nutrients. Then somehow, they knew it was time to hatch. They began to wear ragged circular cuts around the large end of their shells by rubbing the temporary “egg tooth” structure on the top of their bills against the shells’ inner surfaces. Once the cuts were complete, they pushed the two shell halves apart and separated themselves from the empty shells. After a couple of strenuous hours their hatching ordeal was finished. You can tell a nestling has recently hatched if its down is still damp, as the nestling’s in the next photo is.
A newly hatched Tree Swallow looks about as helpless as a creature can get. Tiny, with eyes tightly closed, and naked except for some tufts of down, about all it can do is raise its head on its wobbly neck, open its mouth wide, and wave its pitiful little excuses for wings in an effort to entice a parent to feed it a wad of insects. Simple movements but absolutely vital, for if a nestling fails to perform these behaviors it won’t be fed, and will die.
For the adults, life for the next three weeks will be an almost constant search for food, for themselves and their nestlings, from first dawn to last dusk. Food is all important. Lots of food means fat, healthy, fast-growing young. Little food means the opposite, and little or no food for several days in a row can be fatal. Luckily for the nestlings at Salmon Creek the wetlands around Braddock Bay are rich with flying insects at this time of year. Nevertheless, I’ll be keeping a very close watch on the weather reports for the next three weeks, because if bad weather arrives and lingers, I may need to act.
In case you’re wondering where all those eggshells go, this video from Francois Paquette gives the answer:
And for more on hatching check this web page:
Post 55, June 5
Egg Laying Summary And Hatching Part 2
As of 6/3 egg laying at Salmon Creek was complete. Unless something very out of the ordinary happens, I don’t expect another takeover, and if one of the female Tree Swallows loses a clutch or brood of young at this point, I doubt she’ll renest. In summary, there have been 15 nesting attempts where eggs were laid, and in 14 of those the females laid full clutches of eggs and incubated. In these complete clutches a total of 82 eggs were laid, an average of 5.86 eggs per clutch, which is just slightly higher than the previous nine-year average of 5.79 at Salmon Creek. There were three clutches of 5 eggs, ten of 6 eggs, and only one clutch of 7. I’m actually surprised there weren’t more five egg clutches considering all the adverse climatic conditions the females faced earlier in the season. I guess they were able to replenish their reserves in time for egg production.
This morning, 6/5, it seemed hatching was occurring in every box I checked. Well, almost. Actually, hatching was either in progress or complete at every box now except Boxes 2A, 13 and 14, and Box 13 should hatch tomorrow. This means all twelve “early” nests will hatch within a four-day span. It also means they’ll all go through the same set of weather and feeding conditions, subject to whatever good and bad happens, together. This year is by far the most synchronized of the ten seasons at Salmon Creek.
Adult activity has picked up dramatically as nests that formerly held eggs hold hungry nestlings instead. Both parents are busy now bringing food, not one insect at a time, but mouthfuls of insects each visit, a much more efficient process. The feeding rule for Tree Swallows seems to be one mouthful of insects goes to one nestling each visit – the food isn’t spread around to all the eager little mouths. They will get theirs the next time, or the next, maybe.
For the female Tree Swallows one behavior remains much the same. Before, during incubation, females had applied their brood patches to their eggs to warm them enough for embryonic development to proceed. Now, they apply their brood patches to their tiny, nearly naked nestlings to keep them warm enough for the processes of growth and development to continue. The females will brood their young in this way for several more days and nights, until the nestlings are large enough to maintain sufficient body heat on their own.
When I look in the boxes I see the small nestlings huddling together in a tight ball in the bottom of the nest cup. It’s hard not to view them as some kind of bird “larvae”. And it’s easy to suppose that all those feathers lining the nests are important. In fact, researchers have found that Tree Swallow nests containing lots of feathers do have lower rates of cooling when the females are away. The feathers may also help shield the nestings from excess moisture and ectoparasites. In any event the feathers must be beneficial because experiments that manipulated the number of feathers demonstrated that swallow nestlings grow faster and survive better in well-feathered nests.
Here’s a video from Francois Paquette showing how Tree Swallow adults care for one-day-old young:
And here’s a link to our web page describing parental care of small young:
Post 56, June 7
Trapping And Banding Adults
It’s now four days since hatching began back on 6/3. By this time both females and males at boxes where hatching began earliest should have settled into a comfortable routine entering and feeding their growing nestlings, so I felt today, 6/7, was a good time to start trapping and banding the adults at early hatching Boxes 1, 3, 4 and 9.
Some years ago I took the Braddock Bay Bird Observatory’s Bander Training Program and became licensed to band Tree Swallows, and for several nesting seasons I did band both adults and nestlings at Salmon Creek. I wanted to learn if the return rates of both groups in subsequent years was similar to those reported from other parts of North America, and I found that they were. However, I eventually stopped banding for several years because I didn’t have another specific goal in mind. But within the past year I’ve learned of a major research effort to better understand the details of Tree Swallow migratory movements, including banding operations on their wintering grounds in the US and Mexico. I’ve wondered for a long time where the Salmon Creek swallows winter – my guess is they winter along the central or western Gulf of Mexico coast rather than in Florida, based on migrants’ directional movements here in spring. So, in the hopes one or more of my birds will be recaptured down south, I’m determined to band as many swallows as I can this year.
I don’t use mist nets to capture Tree Swallows. Instead I use a procedure taught to me by Dr. David Hussell of the Canadian Ministry of Natural Resources when I volunteered at his long-term Tree Swallow Study at the Long Point Bird Observatory in Ontario. His trap system consists of simple plastic barriers which are attached temporarily inside boxes using masking tape hinges, and which is propped up with pieces of dried plant stem.
When an adult swallow enters to feed its young its long wings dislodge the stem, causing the barrier to drop down, blocking the entrance hole.
Once an adult Tree Swallow is trapped, I carefully retrieve it, insert it into a cloth bag, and retreat with it to my “field base” where, crouching in the grass, I apply the band, measure wing chord length, and take the bird’s weight. Each swallow’s sex is determined by presence of a brood patch in females or a clocal protruberance in males. And each bird will be aged. All males will be called after-hatch-year (AHY), because all adult males have identical plumage. Females will be labeled either second-year (SY) or after-second-year (ASY) depending on whether they have brownish or blue upper bodies and heads.
Females are normally easy to capture since they are so accustomed to entering boxes rapidly and are so intent on their parental duties. Males can become suspicious of the trap, however, and may be reluctant to enter, and if a male refuses to enter for one hour I’ll remove the trap and won’t try again that day. I don’t want to jeopardize any male’s eagerness to feed his nestlings.
Today is just the start of banding operations here. By the end of the nesting season I hope to band up to 28 adults and 80 plus nestlings. All my pertinent data will be transmitted to the Bird Banding Lab in Maryland, where it will enter the international database of migratory bird information and be available for researchers everywhere to use.
You can learn more about banding Tree Swallows at these web pages:
Post 57, June 9
Brood Reduction Young: The Unlucky Latecomers
As hatching took place in twelve nests during the past week I paid extra-close attention to one thing – did all the eggs hatch the same day, or did one egg hatch a day later than the others? Why this concern? Well, think about the consequences for a nestling that starts off one day behind its nestmates. How will it fare in the crucial competition for food? And the young do compete for food! Those that beg loudest, that display most actively with waving wings and open mouths, and that position themselves closest to the entrance are most apt to receive food on any given parental visit. An unlucky nestling that hatches a day late has had one day less of development and is likely to be smaller and less able to compete. If the food supply is poor there will almost always be at least one larger hungry nestling ahead of it, begging for, demanding, and receiving, the food. The last hatched will often be last fed, will fall farther behind developmentally, and if crunch time arrives, will be the first to die of starvation.
Why don’t eggs always hatch the same day to avoid this problem? The hatching pattern depends on the incubation pattern of the particular species. In some birds (think ducks) incubation doesn’t begin until all eggs are laid, so that all eggs do hatch the same day. At the other extreme, in some species (think owls) incubation starts when the first egg is laid, so each new egg lags behind the ones laid before it, and the brood will have a staggered range of nestling sizes after all have finally hatched. In this latter pattern only the number of nestlings that parents can feed that year will survive – the smaller ones will starve – a system of nestling number adjustment ornithologists call “brood reduction.”
Tree Swallows seem to employ a modified form of brood reduction, in which incubation begins either the day the last egg is laid or one day before the last egg is laid, so some swallow broods will contain one “brood reduction” nestling, and some won’t. I envision brood reduction in Tree Swallows happening in two possible ways. Perhaps a female Tree Swallow happens to acquire excess nutrients within her in a good year, so when her body says it’s time to incubate, maybe she will go ahead and incubate but use those surplus nutrients to produce an “extra” egg the next day. On the other hand, some individual females could simply be genetically “programmed” to begin incubating the day before their last egg is laid, and to follow this pattern every year. I don’t know which, or if either scenario is true, but in any event, when the food supply is good, late-hatched nestlings should do ok, but if food becomes scarce it’s going to be in trouble.
So, after carefully scrutinizing this year’s Tree Swallow hatch at Salmon Creek, here’s what I found. In seven of the twelve “early” nests all eggs hatched the same day, but the other five nests each have one “brood reduction nestling” that hatched a day later than its nest mates. To me, these five nestlings were simply unlucky, but there are a couple of things I can do that may help them survive in spite of this unfair handicap. I can either foster them into other nests with nestlings the same size or, if no suitable nest is available, I can supplement their food to help them reach a survivable size, and these two options will be the subjects of the next two posts.
Post 58, June 11
Fostering: Leveling The Playing Field For Survival
From box checks at hatching I know Boxes 6, 7, 10, 11 and 13 each had a nestling that was smaller than its nestmates simply because it had the bad luck to be last-laid – last hatched. I’ve been very pleased that the small ones in Boxes 6 and 11 seemed to have almost caught up – their parents must be excellent providers – but those in Boxes 7, 10 and 13 had not done as well as of yesterday, 6/9. It’s always been difficult for me to turn away from these “brood reduction” nestlings and “let nature take its course”, and since these little guys were hatched into boxes I put up I feel obligated to do what I can to help them survive.
Sometimes there’s an easy solution. Many experiments have shown that Tree Swallow adults will not reject nestlings from other nests that are added to their brood, so if I can locate another nest with relatively few young that are the same size as a struggling nestling, I will foster it into that nest.
The goal of fostering is to even out the more extreme size differences in nests, by moving either an extra-small or an extra-large nestling into another box having nestlings its own size. I try to foster small nestlings while they’re still relatively young, around four or five days old, before the effects of nutritional deprivation stunt their development severely. My first choice is to use foster nests that have fewer nestlings to begin with, and when I find such a nest where I think the parents can safely accept another mouth to feed without jeopardizing the health of their own young, I take the nestling to that box for a size comparison. If there’s a match the foster youngster is wished well and put gently into its new home, but before I do, I put a temporary non-toxic ink mark on one of its legs to identify it, because I want to track the success of its fostering.
This year there was only one good opportunity for fostering, but it should help the situation at both Box 7 and Box 10. Box 10 had an unusual situation. One egg hatched on 6/5, three more on 6/6, and the last on 6/7, so the resulting brood had one relatively large nestling, three intermediate-sized, and one small one that hatched two full days later than the first. Over in the other box, Box 7, five nestlings hatched on 6/5 and one on 6/6, with the result seen in the first photo of this post.
My plan was to even things out in both nests by fostering the largest nestling from box 10 into Box 7, where it will be with nestlings its own size, and to foster the smallest nestling from Box 7 into Box 10, where it should have a much better chance to survive. Yesterday morning, 6/10, I carried out this simple one for one swap.
Unfortunately, I can’t always find suitable foster boxes for needy nestlings, and this is the situation for Box 13. But there is another option, one that’s nowhere near as good as fostering, but still better than nothing. I can hand-feed this nestling extra food each day until it’s twelve days old, to try to boost it closer to the developmental level of its nestmates so it can compete better with them for food brought by its parents.
Post 59, June 13
Supplemental Feeding Of Tree Swallow Nestlings
This is what I love to see, sunny skies and swallows carrying lots of food to their young. But there are times almost every year when some Tree Swallow nestlings at the grid don’t get sufficient food and fall behind developmentally as a result. And if there is no suitable nest into which they can be fostered I feel compelled to handfeed these needy nestlings a couple times per day until they reach the twelve-day old limit for safe handling. I also hand-feed every nestling at the grid between about 4 days and 12 days during prolonged severe weather, just to help them survive until the feeding improves. Thank goodness this doesn’t happen every year!
This season I began supplemental feeding on 6/11. I’ve been feeding the smallest single nestling in Boxes 3, 5, 6, 7 and 13, and the two smallest in Box 10. Some of these are brood reduction young and some seem to be lagging a bit for other, unknown reasons, but since I have food, I’m feeding them all.
Since Tree Swallows nestlings are normally fed insects by their parents, I do the same. Mealworms, which are actually the larvae of a flour beetle, are my primary food source, since they are generally available at pet stores and not expensive. I keep live mealworms in plastic containers with small holes in the lids for ventilation. For their food I use a mix of flour and crumbled bran flakes, with slices of raw potato as a moisture source. I often keep some of the mealworms refrigerated so they won’t mature into beetles too quickly.
For detailed information on every aspect of mealworm feeding and culture visit the outstanding bluebird web site Sialis at:
When I feed nestlings, I take the number of mealworms I expect to use with me to the grid in a small container. I also bring another small container with water to which I’ve added soluble bird vitamins and minerals.
At the grid I pick a spot 100 feet or more from the box containing a nestling to be fed. There I prepare some mealworms by dropping them into the water mix, which they absorb. This will give the nestling hydration, nutrients, vitamins and minerals all in one package. Then I remove the nestling or nestlings to be fed from the box and return to the feeding site. If I happen to be feeding all the nestlings at a box, as I may do during bad weather, I only remove half the brood at a time. I never want parents to see an empty nest, for fear they’ll desert, thinking the nest has been predated. (All photos of complete broods that you see on this narrative were taken next to the box, so parents would not enter and see empty nests).
A young Tree Swallow seldom begs when hand-fed, so one must gently use a fingernail to open its bill, and then insert a mealworm head-first into the back of its mouth. At this point the swallowing reflex usually takes over and the bird gulps the mealworm down with bobbing motions of its head and neck.
I give nestlings a couple of minutes to rest before offering more food. Then the process is repeated until the nestling wants no more, which it shows by shaking its head and spitting the food out. A nestling is never forced to eat if it clearly doesn’t want to.
One feeding usually consists of from one to four mealworms, depending on the size and hunger level of the nestling. Then I move on the next box with a needy nestling.
Once I’ve completed a round of feedings I’ll do something else for an hour or so. Then I repeat the circuit of feedings. It’s time consuming and messy, and the parent swallows really aren’t thrilled by my intrusions, but I always feel good having done it, and I truly believe supplemental feeding has saved many nestlings over the years.
Post 60, June 15
My, How You’ve Grown! From Hatch to 12 Days
After all these years it still amazes me how rapidly those tiny newly-hatched, “larval” Tree Swallows transform into actual birds, creatures that look, sound and act like real birds. From 1.5 grams to 20 plus grams in 12 days! From nearly naked to semi-feathered. From eyes-closed blind to eyes wide-open and world-inspecting. From barely audible peeps to rapid-fire chatterbox begging machines. From being unable to keep warm to being fully able to thermoregulate. From appearing to be all belly, mouth and feet, to achieving birdlike body proportions. The list goes on and on, and it really is truly amazing.
Tree Swallow nestlings grow so fast I have to keep reminding myself to take photographs, because if I don’t there’d quickly be none to photograph at the earlier stages. They would have all shot past already!
It would be nice to be able to say “this is what a 6-day old Tree Swallow nestling looks like”, but it isn’t as easy as you might expect, because swallows in different nests often grow at somewhat different rates. For instance, those in small broods tend to grow faster than those in large ones. Poor weather conditions or sub-optimal foraging habitat can retard development. Parental age and foraging ability differences may affect nestling growth. Parasites can occasionally depress growth rates. Genetic variables may come into play. And to further complicate matters brood reduction and poor feeding can produce a range of sizes within a single brood. So, it might be best to consider trends or averages, rather than state something always happens by such and such a day after hatching.
Having said this, here are some things I expect to see as the nestling Tree Swallows grow and develop at the Salmon Creek grid:
By day 3 or 4 the “tracts” where feather growth will be concentrated are clearly visible as darkened areas in the nestlings’ pinkish skin.
Between about day 5 and day 7 eye slits open.
By day 7 or 8 flight feather sheaths usually protrude from both wings and tail like little quills, and smaller sheaths show where body contour feathers are erupting. You’ll also note how much a nestling’s wings have enlarged and elongated in these few days since hatching.
As feathers continue to erupt out from the ends of their sheaths each looks like a little paintbrush. This is most noticeable on the wings and tail, but can also be seen on the body’s contour feathers.
By day 12 it’s pretty clear we’re dealing with actual birds here. The light-yellow flanges bordering bills, while still evident, aren’t the dominant features they were a few days ago. Eyes are bright and alert, well aware of their surroundings. And as their feathers have grown and their downy ends shed nestlings definitely look more birdlike and less reptilian.
12 days post-hatch is a milestone in my relations with nestlings. My in-hand examinations of nestlings must stop at this point because nestlings older than 12 days become more and more apt to jump out of their box if disturbed, and if they do so before they can fly strongly odds are they will die. Therefore, any observations I make after day 12 must be done from a safe distance. But before day 12 is over there is one last thing I’ll do – I’ll be giving each nestling that has reached that age a shiny new band.
Here’s a link to our web page describing nestling growth to day 12:
And here are three videos from Francois Paquette covering the day 1-12 period. The first shows how typical physical development and behaviors change during this time.
In the second you can watch how parent Tree Swallows feed their young and try to keep the nest sanitary by disposing of the fecal sacs the nestlings produce.
And the third demonstrates how the female’s brooding behavior changes as her young gradually become able to keep themselves warm.
Post 61, June 17
Banding Nestlings And The 12 Day Limit
I’m really a smelly mess! I’ve been banding 12-day-old Tree Swallows the past three mornings, a total of 70 banded so far. Plus, each day for a week I’ve been supplemental feeding ten or so of the littlest guys. My shirt tells the story – it’s covered with swallow poo stains. I anticipated this and have been wearing the same old raggedy thing each time I go to the grid to band. That shirt is headed for the trash bin as soon as this is finished. No wonder no one wants to band with me!
Banding nestling Tree Swallows is much simpler than banding adults. Nestlings don’t have to be trapped and there aren’t a bunch of measurements to take. They can’t be sexed by appearance and their age is already known to the day. Banding nestlings would be easy if they weren’t such squirmy little critters and their legs weren’t so short.
But there is one extremely important thing that banders must know about Tree Swallow nestlings. They should only be banded on day 11 or 12 post-hatch. At younger ages nestlings’ legs are swelled with fatty tissue which a band could constrict, potentially interfering with circulation. Perhaps more crucial is the fact that nestlings older than 12 days may jump out of their boxes after handling, and if they can’t fly strongly they will die uncared-for on the ground. This is the reason most Tree Swallow research includes strict protocols restricting experimental handling of nestlings older than 12 days, and this is the reason I’ve emphasized repeatedly on my web site that boxes suspected of containing older nestling Tree Swallows should not be checked or even approached. Thank goodness for Control Sheets – they pinpoint the ages of nestlings in each of my boxes, so I know exactly when I can band and when I must keep away.
So the 12 day limit dictates that I’ve touched those 70 banded nestlings for the last time. I can’t help them any more – no more supplemental feeding or fostering for them. I won’t even go near their boxes during the six to eight days that remain before they fledge. Ooops! There is one exception to the 12-day limit. If I thought a box was mite-infested, and approached the box very quietly and carefully from the back or side, and confirmed there were mites swarming at the entrance, I would be forced to intervene to try to save the nestlings’ lives, regardless of their age. For info see:
Will these banded nestlings return to Salmon Creek next year? If they were adults I would expect to see a third to half of them again. But even though I’ll band over 80 nestlings I don’t expect to see many of them again, and I may not see any at all, ever. For one thing juvenile mortality is generally quite high, and unfortunately many of these nestlings will perish on migration or on the wintering grounds. And those that survive and migrate north next spring as SYs will find my nest boxes already claimed by older adults. So, the nestlings, now SYs, will either have to float in the neighborhood, battle for a box, or move on. Actually, research has found that nestling Tree Swallows do tend to return to the area where they were raised rather than disperse farther afield, so my banded nestlings that survive may be present at Salmon Creek next year, but probably as floaters, not nesters. And if they float I won’t catch them in my box traps, and I won’t really know if they’ve returned or not.
So, why should I bother banding nestlings at all? I stopped banding both adults and nestlings several years ago and didn’t resume until this year, but even with this major gap I know some banded nestlings have returned to Salmon Creek and bred. It’s occurred a minimum of five times. For instance, this year’s Box 4 female, banded here as a nestling, is her fifth season as a breeding-age adult. I’ve begun banding nestlings again this year partly out of curiosity to see who will return in the future. But, more importantly, as I mentioned in an earlier post there is a coordinated effort to better understand the migration routes, stopover roosts and wintering ground locations and behavior of Tree Swallows, and the more birds banded and recaptured the better these details may be understood. And the more adults and nestlings I band the higher the chances Salmon Creek swallows will contribute to the knowledge generated by this study.
For more on banding nestling Tree Swallows see:
Post 62, June 19
Who’s Your Father? Extra-Pair Paternity In Tree Swallows
These six young Tree Swallows are from the same nest and hatched from eggs laid by the same mother, but you’d never guess by looking that odds are at least one and possibly even most were fathered by someone or ones other than the resident male who’s been working so hard to feed them. Yes, it’s true, researchers have found that Tree Swallows have high rates of what’s called “extra-pair paternity.” What’s going on here???
For possible explanations we need to go back a bit in the Tree Swallow breeding cycle to the period just before and during egg laying, the period when all that mating activity was taking place. You’ll remember that a male wanting to mate would give the “tic call”, land on a female’s flattened back, grasp her head feathers in his bill, and rotate his cloacal protuberance under her tail to contact her vent and transfer his sperm to her. What I didn’t mention was that females can prevent mating from happening simply by flipping their tails up, making it impossible for males to land and copulate. In other words, females are in charge of whether a male’s copulation attempts succeed or fail. This means females can mate whenever and with whomever they choose. A female is free to select the male or males whose sperm will fertilize her eggs, and she doesn’t have to pick the male at her nest box.
You can view a short video of a female Tree Swallow rejecting a male by clicking here:
Ornithologists have learned through DNA testing that some or even most of a female Tree Swallow’s brood may have different fathers. And I hope I don’t shatter anyone’s illusions when I say Tree Swallow females aren’t alone in mating with males they aren’t paired with. It’s probably safe to assume most of the females of your favorite songbird species permit and may actively solicit copulation with other males. That’s right, your female bluebirds, cardinals, chickadees, etc., all show this behavior to varying degrees.
The big question of course is why? Why do so many female birds elect to mate with males they aren’t paired with? Extra-pair copulation must bestow some kind of advantages or it wouldn’t be so widespread. One often proposed hypothesis is that females are seeking “good genes”; that somehow they can evaluate male “quality”, and if their own male resident partner doesn’t quite measure up females go looking elsewhere for sperm donors. Another idea is that females “want” a variety of different genetic combinations in their offspring, because this may result in better odds of her having at least some descendants which are genetically equipped to cope with future changes in their world. As appealing as these ideas are, they’ve turned out to be extremely difficult to prove, and our knowledge of the ultimate causes of extra-pair paternity in birds such as Tree Swallows remains incomplete. However, one revelation from all this research is that, while female Tree Swallows sometimes mate with other males that possess nest sites, they also will mate with non-resident floaters. In other words, unlike females, male Tree Swallows don’t need to possess nest cavities in order to reproduce. And this leads me to the topic of the next post, which will be why I think SY male Tree Swallows are blue, not brown.
Post 63, June 21
Ridiculous Idea #2: Why I Think Second-Year (SY) Male Tree Swallows Are Blue, Not Brown
Earlier in this narrative (Post 50) I proposed a ridiculous explanation for why I thought it was advantageous for second-year (SY) female Tree Swallows to have a unique brownish sub-adult plumage at this one time of their life. Now I’ll try to explain why I think second-year male Tree Swallows are better off not having a sub-adult plumage, why all males have identical plumage after they molt their juvenile gray feathers, whether they are in their second calendar year of life or their tenth. However, once again I have to admit no one of any repute has ever agreed with this ridiculous idea either.
Why are SY males blue instead of a sub-adult brown like females? I believe there must be reasons for oddities like this, and in this case I think everything depends on the fact that, unlike females, male Tree Swallows can reproduce without possessing a nest cavity. Floating males of all ages can mate with females seeking extra-pair copulations, and can father young with these females. The only contribution these floating fathers make is their sperm – they don’t know if they have offspring or who they are, and they certainly don’t help raise any young they might father.
So, here’s the scenario. A second-year male Tree Swallow, migrating north for the first time, arrives on the breeding grounds to find all or almost all nest sites are already claimed by older males that arrived earlier. He is probably doomed to float this year. But if this SY male can appear to be of “high quality” to females, he can still become a father through extra-pair mating. So what possible advantage could there be in wearing a sub-adult plumage that labels him and perhaps stigmatizes him to females as young and inexperienced? Wouldn’t a high quality SY male’s chances of extra-pair mating be better if he appeared identical to and therefore as able as older males who were proven breeders and survivors? I suspect (but can’t provr) that high quality male SY Tree Swallows that look like older males are more likely to reproduce, so there is selective pressure for SY males to “mimic” the bright blue color of older males rather than wear a sub-adult brownish plumage. So, there it is, another ridiculous idea from yours truly.
Post 64, June 22
This Is A Year For The Record Book So Far
This year turning out to be one for the record book at Salmon Creek. The last egg in the last box, Box 14, hatched on 6/20. Of the 86 total eggs laid this year, four were covered over and died in the Box 2 takeover, but of the 82 eggs that female swallows actually incubated only one failed to hatch! This 81-egg hatch is the largest ever here, and the 94% hatch rate for eggs laid beats the previous record of 90%. Not surprisingly the average brood size was also a new high – 5.78 young per nest at hatching – far above the 4.97 young per brood average of the last nine years. And of the 70 nestlings that hatched in the twelve earlier boxes, all 70 made it to the 12-day limit, which made me very happy indeed! We were extremely lucky we missed the cold rains that caused such terrible losses among cavity-nesting birds elsewhere in the northeast this spring. I am concerned about the two late nestings though. Both Box 2 and 14 have brood reduction nestlings, and at this time I cannot enter the grid to feed mealworms to either of them for fear of disturbing older nestlings in nearby boxes into fledging prematurely. I’ll need to reassess this situation in a few days, after fledging is complete in the early 12 boxes.
In considering possible reasons for the record low egg mortality in 2012 the only thing that really stands out was a ten-day period of warm to record hot days during the first ten days of this year’s highly synchronized incubation period. I know from experience that persistent cold during incubation often correlates with higher egg death, so perhaps persistent heat during incubation increases the chances of smooth and complete embryonic development within the eggs.
The biggest impact of this year’s large average brood size was that it limited the possibilities for fostering brood reduction young. Most years there are at least a few small broods of three or four young, whose parents could easily accept fosters struggling to survive in larger broods. But this year the smallest natural brood was five, and there weren’t many of those. The best I could do was one for one swaps – the largest in a brood of smaller-sized nestlings for the smallest in a brood of larger-sized nestlings. I did this first between Boxes 10 and 7, and later, when it was apparent the smallest in box 6 was failing, I swapped it for the remaining largest in Box 10. In this way Box 10 came to contain three brood reduction nestlings, its own and those from Boxes 6 and 7. I’m glad to report that when I banded nestlings at 12 days all four fostered young appeared to be thriving. There were a couple of other brood reduction nestlings I would have liked to foster, but since there were no suitable nests for them I supplemental fed them as best I could until the day 12 limit.
On another front the trapping and banding of adults is finished. All 14 resident females were banded and nine of the males, so 23 out of 28 adults wasn’t too bad. As expected, some of the males were trap-wary, and refused to enter their box until I removed the trap, which I did as soon as it was clear they were too clever for me. What was not expected was that the “Big Guy” in Box 8 figured how to lift the trap flap and escape – and he did it twice! What a smart fellow!
On a sadder note, the male with the diseased foot that had originally claimed Box 3 (see Post 26) was not the male captured and banded there. The original male has vanished from the grid, presumably driven away. Nature is not kind to those with disabilities, and there was nothing I could do to help him.
Post 65, June 23
We’re In The Home Stretch: Tree Swallow Nestlings Get Ready To Fledge
The changing situation at the Salmon Creek grid has forced me to alter my own behavior. As I’ve stressed before, Tree Swallows nestlings become more and more prone to premature fledging – jumping out of boxes if startled before they can really fly – once they’ve passed about 12 days of age, and the nestlings in all twelve early boxes are well past that point now. Since I don’t want my actions or presence to disturb them or their parents my days of box checking, supplemental feeding smaller young, and sitting in the grid observing are over until all the larger living nestlings do actually fledge. So I can’t venture far into the field from the hedgerow now, and I watch boxes through binoculars, which I seldom use until nestlings reach this stage. As a result any photos I take must be shot from a distance and only at boxes on the grid’s edge whose adults I know aren’t overly excitable, hence the poorer than usual photo quality.
I must also apologize for not being able to take photos documenting the important development steps and behavior of the nestlings occurring inside the boxes between nestling day 12 and their eventual fledging at between day 18 and 22. However, Francois Paquette of Quebec has graciously provided in-box video demonstrating most of the basic steps. There will be links at the end of this post. Merci, Francois!
The most unmistakable sign that fledging is fast approaching is the sight of nestlings leaning out box entrances, waiting for their food-bearing parents. It’s hard to hear it from a distance but when nestlings spy a parent gliding in they let out rapid staccato begging cries – “feed me!” “feed me!” “feed me now!!!” The parents are working harder and harder to meet the needs of all these adult-sized young, and I wonder sometimes what the presence of 109 adult and nestling Tree Swallows is doing to the local flying insect populations.
Where parents formerly ducked into the boxes to feed their young, now the food transfer is very rapid and usually takes place at the entrance, sometimes with the parent landing but often not.
One consequence of older nestlings meeting their parents at the entrance is that parents seldom are able to enter the boxes anymore, meaning among other things that nestling feces don’t get removed. The bottom of a box with five, six or even seven large nestlings being pumped full of food all day long can become very messy, one reason why it helps to use boxes with spacious interiors so at least some fecal material is deposited on the outer edges of the nest, not on top of other nestlings.
Here’s a video showing changes in the manner older nestlings are fed:
Another reason why large box interiors are desirable is that older nestlings begin to exercise their wings as they near fledging, provided there is room in the box. They grip nest material with their feet and beat their wings as fast as they can for bursts of several seconds at a time. Those of you with in-box video cameras have probably witnessed this behavior. I have to believe this is an important preparation for fledging, when young swallows must be able to fly strongly from the moment they leap from the box. Nestlings fledging from cramped little boxes cannot be as well prepared, and I believe their chances for surviving may be diminished. In the next video you can watch older nestlings attempting to flutter their wings in a small box.
For me, these last few days before my swallows leave their nests can be a time of racked nerves and crossed fingers. A blast of cold, wet, windy weather could be a disaster. I almost ended my involvement with Tree Swallows many years ago after an event like this wiped out nearly all nestlings in the 18 box project I operated at the time. As it was I quit for nearly ten years. And there’s always the threat that deliberate or innocent human disturbance could cause mass premature fledging. I won’t sleep well until the whole bunch is airborne.
To see some really good photos (taken from blinds by real photographers) of older swallows begging and food being transferred from adult to nestling see our web page covering older nestling development from day 13 to fledging:
Post 66, June 25
Most Nestling Tree Swallows At Salmon Creek Have Fledged
Yes, it’s been awhile since the last post, but there’s a reason. I didn’t have anything to report. As fledging neared my visits to the grid became very brief, and some days I stayed away altogether, for pre-fledging is a time for human patience and restraint. On several days all I could do was scan the distant boxes from the hedgerow through binocs, trying to see which boxes still contained nestlings crowding the entrances or being fed by parents. And of course I have no photos of what was going on inside the boxes during the nestlings’ last few days of residence, but once again I’m grateful for within-box video from Francois Paquette: links at the end of this post.
Finally today, 6/25, it appeared that most boxes were empty and not being attended, so I was able to make a partial inspection of the grid, carefully avoiding Boxes 5, 10, and 13 where nestlings near fledging could still be seen peeking out.
In nine boxes I found well-used nests and no dead nestlings, just what I’d hoped to see. A total of 52 nestlings have fledged, so far. Box 2A, one of the two late boxes, contained six nestlings 9 days old that appeared to be doing well. But a sad discovery waited in late Box 14; all five nestlings had died at roughly day 4. Since there were no signs of injury and no swarm of mites, my guess is that one of the parents, most likely the female who would have done all the brooding and much of the feeding, had died or deserted for unknown reasons, followed by desertion by the other adult. Unfortunately, late nests often seem more problematic and desertion prone.
I wish I had some neat photos or videos of the act of fledging itself, but the best I can do is describe it briefly based on past experiences. As the big day nears many of the food transfers from parent to nestling are made at the entrance without the parents alighting. At times the parents seem to hover in front of the nestlings, as if enticing them to fly. Eventually the moment arrives when the nestling launches itself into the air, and if it has been allowed to develop and mature fully in the box it should be able to fly with relative skill and confidence from the very start.
As the excited fledgling flaps to stay airborne it usually calls loudly, which draws every swallow in the vicinity to it. The other swallows pursue the fledgling closely, seeming to drive it along. This group behavior has been interpreted in different ways. Some people believe the other swallows are chasing and harassing the fledgling, attempting to force it to the ground. Others feel the pursuit spurs the fledgling to keep flying until it reaches a suitable above-ground perch, that it is a behavior all adults participate in instinctively, with the “expectation” that when their own nestlings fledge they will receive group “encouragement” too. Personally, I support the second viewpoint, but nothing has been proven to date.
In some case new-fledged swallows seem completely independent from the start, but it’s more common for them to be fed by parents for a few days after leaving the nest.
Some years the air above the grid and the surrounding fields and wetlands are filled with Tree Swallows, some adults, but mostly newly-fledged juveniles in their dapper silky gray and white plumage. But in other years, including this one, most Tree Swallows have left the grid area almost immediately. The few juveniles I saw this morning could be distinguished quite easily from adults. Though they weigh as much as older birds these juveniles’ wing feathers are still growing and are usually only about 85% as long as their parents’ at fledging. Until these feathers are fully grown the juveniles’ flight is noticeably more fluttery and moth-like. I love to watch these young swallows wheel and bank, soar and dive, flap and glide. At the risk of sounding anthropomorphic I like to think they are “enjoying” their flying abilities.
Some of the juveniles that remained at the grid this morning were moving from box to box, peeking in and investigating in typical juvenile fashion. They seemed particularly drawn to boxes still containing nestlings. Juveniles checking out boxes can be downright pesky sometimes, and can interfere with parents trying to feed young. I hope this wasn’t a cause of parental desertion at Box 14.
Now for some links. First are two pages from our web site, one on fledging and one on independent juveniles:
The second group of links lead to videos showing life inside a box for young ready to fledge and then the actual box-leaving for the six nestlings:
Post 67, June 28
Fledging Update 2 And The Late Nest
What a difference! From 14 active nests to one in just a few days’ time. From 109 resident Tree Swallows down to 8. And while the parents of the remaining late nest at Box 2A were working to feed their six young, I’ve been dismantling the rest of the grid for the year. First wipe the grease off the poles and remove the predator guards. Then take each box off its pole and remove the old nests. Finally, dig the poles out and replace the supporting rocks at the surface of each hole so I can relocate them next spring. Oh, and lug everything across fields and hedgerow to my car for the ride home for box washing and disinfecting, and equipment storage. I sure wish I didn’t have to go through this ritual each year – I’m getting too old for it. I did decide to leave Boxes 3 and 4 up a bit longer – they seem to be favorite sunning and preening perches for those swallows that remain.
The fledging report is in for Boxes 5, 10 and 13 – all their nestlings lived to fly, bringing the total to an even 70 young produced this year, with a possibility of six more if those in Box 2A make it. This last brood looked good at 9 days old on 6/26, but I’m getting nervous about disturbing the parents. I’ve been giving the box a wide berth, because I feel the adults’ instinct to care for their young is now competing with a growing urge to join the flocks at the big upstate NY marshland complexes where this region’s Tree Swallows stage for weeks or months prior to migration. I suspect adults at late nests become more prone to desert as summer advances, and since I don’t want to be the cause there’ll be no more box checks and no banding of nestlings at late Box 2A.
I have to say Box 2A looks pretty isolated, but it is seldom alone, for passing juveniles are drawn to boxes containing nestlings as if by magnets. They perch on the roofs and at entrances, and sometimes even enter the boxes, and they must be a real nuisance to the parents at times.
However, this last set of parents may have an advantage over the earlier nesters because the immediate grid area has far fewer Tree Swallows to feed now that so many adults and juveniles have left. Perhaps the Box 2A parents won’t have to search quite so hard for flying insects to feed their brood during the week or so until they finally fledge around 7/5. Oh well, I’ve stalled around long enough. It’s time to wash and disinfect the boxes I took back to the house for off-season storage.
Post 68, June 30
The Season Summary And Assessment
At the conclusion of each Tree Swallow nesting season I take a look at the overall performance of the Salmon Creek Nest Box Project grid, trying to determine what went well, what went poorly, and whether the results could point to ways of improving things for the birds in future years. So, let’s start.
This has been an unusual year here at Salmon Creek in many respects. It started with the entirely unexpected very warm spell in March that encouraged large numbers of Tree Swallows to push north prematurely. I was able to get eight boxes up to receive them at a time when snow drifts normally would have covered the frozen ground of the grid field. Some of the early arrivals undoubtedly met their fate when normal seasonal cold returned, and there was evidence of repeated communal roosting, a bitter weather survival tactic, in several boxes. Unfortunately, several feeding experiments performed during the poor weather were total failures, and I doubt I’ll try again.
It became clear early on that eight boxes weren’t going to be enough this year. Where in some years a few surplus swallows floated the grid, this year there were small flocks of “extra” Tree Swallows almost from the start. These gathered in the field, just waiting signs of weakness among the successful box claimants.
I added four boxes at a very early date, but after witnessing several takeover battles that showed even these extra boxes hadn’t completely eased the competition for nest sites, I put up two more, for a total of 14 boxes, the most ever at this grid. Although I have other boxes, of different designs, I don’t want to exceed 14 in the future. In fact, I’d like to keep the grid down to a more manageable 8-10 boxes if possible, but floater numbers will continue to dictate number of boxes offered.
Because the early spring plant growth in the field obscured last-year’s dried vegetation, the later-nesting females were offered dried grasses placed on the ground below their boxes as an experiment. They were extremely quick to take advantage of this convenient supply, building their nest bases to complete cup stage so rapidly that the first four later nesters caught up with the eight early nesters within a few short days. When egg laying began these twelve nests had first eggs within a six day span. This set the stage for a very synchronized nestling period, which in most years should be a good thing, so I’ll continue to offer nesting grasses in future years.
White Mute Swan feathers, which in past years were the feathers of choice for lining Tree Swallow nests, were apparently scarce this year, suggesting measures to “control” swan numbers had taken a lethal turn. Most of the grid nests were lined with Canada Goose or Mallard Duck feathers this year.
Warm, dry weather was the rule for the second half of the breeding season. The incubation period was favored with so much warmth that egg death was limited to just one egg out of 82, and that egg could have been infertile from the start. An additional four eggs died in Box 2 when the original female was evicted in a takeover and her partial clutch covered over.
Hatching percentage and brood size set new records, and in the twelve early nests every nestling that hatched lived to fledge. This outstanding performance was likely due to the mild weather and good parenting, but I believe fostering swaps of brood reduction nestlings into Box 10 saved two lives, and I also think supplemental feeding of mealworms to the ten or so smallest nestlings improved their chances for survival.
There was one complete brood loss – in Box 14 all five nestlings were found dead at about 4 days post-hatch. Although there’s no proof I suspect the female either died or deserted, followed soon after by desertion by the male. If the male had left first, I would have expected the female to try to raise her brood on her own, as females are known to attempt. That this nest failure occurred in the last nest to be initiated might indicate this female had a weakness of some sort that had caused her late nesting start, and that might also have led to her death or desertion. In any case the nestling deaths in Box 14 were disturbing exceptions to an otherwise very productive nesting season at Salmon Creek.
After a lapse of several years a major effort was made to capture and band the adults at the grid, and 23 of the 28 were processed. And all living nestlings were banded at day 12 except the late brood in Box 2A. The hope is that some of these birds will be recaptured on migration or on the wintering grounds, and contribute to the knowledge of this species’ movements during the non-breeding seasons. I plan to continue banding in the next few years.
As of this writing on 6/30, 70 of the 81 nestlings that hatched have fledged, and the last six in Box 2A are in their 14th day post-hatch and being attended by both parents. The overall reproductive success of the Tree Swallows at Salmon Creek should be good to very good, depending on the fate of these last six young. If all goes well, they should fledge in another four to six days, and follow their fellow independent Tree Swallows away from the grid. All things considered it’s been a pretty good season, for them and for me.
Post 69, July 2
Why I Wrote This Blog
On the very first post of this narrative, back on 3/13, I said my purpose was to “give you real insights into the behavior, biology, and ecology of these super little songbirds”. True, but it shouldn’t be a surprise that I had a bit more in mind, and as the blog nears its end now’s a good time to fess up.
I hoped for a wide audience, one not limited to serious bird enthusiasts, for Tree Swallows have such a large geographic breeding range and are so approachable that they can potentially be managed by a great diversity of people. So this blog was meant for farmers in Alberta, villagers in New Hampshire, teachers in Missouri, watershed restorers in California, bluebird hobbyists in Kentucky, fishermen in Quebec, homesteaders in Alaska, students in Virginia – well, you get the picture. Since Tree Swallows can be seen and enjoyed by so many people across most of North America, people of all ages, professions, and backgrounds, I wanted to reveal and emphasize what an easy species this is to attract, how visible they are, and what an ideal species this is for anyone seeking to learn about birds. I wanted to share with as many people as possible how experiences with Tree Swallows could enrich their lives and help them connect with nature, as the swallows have for me.
I also wanted very much to give readers a sense of the basic issues and hardships songbirds in general and Tree Swallows in particular confront and endure in order to reproduce, to raise awareness of how complex bird lives are. And while I’ve tried to keep the tone casual and not overly technical, I still wanted to at least introduce some aspects of bird life you may not have been aware of, things like how critical limited resources can drive behavior, the existence and prevalence of extra-pair paternity, the way brood reduction operates, etc. I thought you might be interested; I know I am and I think I’m probably like you.
I intended the blog to present some guiding principles of wildlife management, things I think should be common sense, but that are ignored or overlooked so often by people who should know better it makes me cringe. Little things like realizing management should be for the benefit of the life forms managed for, not for the person managing. That to manage successfully for a species one really ought to learn its habitat requirements and its behavioral needs. That to attract a species without considering predator exposure is unconscionable. That if there are techniques to minimize both intraspecific and interspecific competition they should be utilized. That if there are methods to intervene to save individuals without compromising the larger number, those methods should at least be considered. Sorry if I’m getting preachy – I expect you all know this stuff, at least on an intuitive level, but just in case you didn’t before I wanted the blog to expose you to these principles.
On the other hand, I’ve sincerely tried to convey the message that establishing and operating Tree Swallow grids isn’t rocket science. I want to stress that there’s nothing I did at Salmon Creek this year that you couldn’t do, not one single thing. From the very beginning my most important goal for this blog was to encourage you to start your own Tree Swallow project, even if that means just one box, and if you are already working with Tree Swallows to consider expanding your scope. I don’t use my own land; I don’t have a big workshop of power tools; I don’t have a big budget, and you don’t need them either. I’m almost completely self-taught, and you can go that route too, but you don’t have to – you can refer to the my handy web site, www.treeswallowprojects.com, for just about everything you need to know, and if it isn’t there, you can contact me directly and I’ll try to help. I want you to have an intimate, rewarding wildlife experience with Tree Swallows. I want you to go ahead and give it a try.
Lastly, I knew this blog would be a testament to my passion for Tree Swallows. Way, way back in 1973 I put a few crude boxes up on a piece of rural land almost as an afterthought, not even knowing what might nest in them. And here I am decades later finding myself learning more about Tree Swallows almost every day, writing about them, advocating their conservation and expounding their many virtues to anyone who will listen. Yeah, I expect I’m obsessed, but these little birds fascinate and inspire me. I really do love Tree Swallows, and I’m not ashamed to let the world know it!
So that’s why I wrote this blog.
Post 70, July 6
One Last Report and Two Thanks
After staying completely away from the Salmon Creek grid for several days I took peeks from the hedgerow on both 7/4 and 7/5, which were days 18 and 19 for the nestlings in the last active Tree Swallow nest in Box 2A. On the 4th I could see from the distance there were nestlings poking their bodies out of the box entrance. On the 5th there was still at least one nestling in the box but three or more newly fledged swallows, presumably from that box, were giving begging calls as they zipped over the field with a flock of other juveniles. Finally, today, 7/6, seeing no nestlings at the entrance, I ventured out and found Box 2A was empty at last. The last of the six nestlings had fledged, the 13th completely successful brood.
The final numbers for the 2012 season are 76 nestlings fledged out of 86 eggs laid and 81 nestlings hatched. The percent of eggs laid that produced fledged young, 88%, was far above the nine-year average of 67%, and the percent of nestlings that fledged, 94%, was slightly above the 92% average. If it weren’t for the nest failure in Box 14, I’d be extremely happy with the season’s results.
So, this year’s nesting season at Salmon Creek has ended, and since this is the concluding post for this blog, I want to offer two thanks. The first is to Tree Swallows, for they have taught me so many, many things over the years, and in doing so have challenged me to think and introduced me new ways of learning. How impoverished my life would have been had I not become involved in theirs.
The swallows taught me how to step outside myself and see the world through another species’ eyes, to analyze it, to see the struggles and how they are coped with. They let me glimpse the interconnectedness of all things, the living and the non-living. They taught me that careful preparation is the foundation for success, but sometimes bad things happen even then.
The swallows have taught me that life is a precious gift, tenuous and to be valued while we have it. That while some are born and live, others die and are left behind, and the difference between the two outcomes can be unpredictable and out of our control.
Through the swallows I have learned that one species can teach about many and that in the final analysis my life issues aren’t so very different from theirs. In trying to understand their lives I better understand my own, though of course I’ll never comprehend it all, theirs or mine.
The swallows have taught me that while sometimes I can help there are other times when I must step away.
They have made me more aware of the world, the movement of air, the warmth of the sun, the bite of the wind, the constant interplay and changing of natural processes and forces. They have made me more open to seeing the insect in flight, the flea in the nest, the wave of a nestling’s wing, the world in detail and as a whole.
Tree Swallows have helped me experience the joy of reunion and the bittersweet of parting. Return if you can. I’ll be waiting for you.
My second thanks is to you, the inquisitive, concerned, good-hearted readers of this blog. Thank you for your interest in Tree Swallows – I hope this season’s story has answered some of your questions and made you want to learn more about these wonderful birds, for trust me, this account barely scraped the surface.
Thanks to those of you who have contacted me directly, who have shared your experiences and photos. When you’ve had problems I’ve enjoyed trying to solve them with you, and sometimes we succeeded, didn’t we?
Thank you for continuing to be interested in and concerned for birds and other wildlife, and the world as a whole, for it is truly a whole. Perhaps together through our actions we can make a difference and advocate for change where it is needed.
And now I close this narrative. If you’ve enjoyed it half as much as I’ve enjoyed putting it together, it’s been a success.
So long from Salmon Creek,