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 2.  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 Box 2, 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 2 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, the 2012 nesting season at Salmon Creek has ended, and since this is the concluding post for this blog, I want to offer two sets of 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 would my life 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 analyse 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 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 blog has answered some of your questions and made you want to learn more about these wonderful birds, for trust me, the blog only 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 blog.  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,

Chris Gates

On the very first post of this blog, back on 3/13/12, 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, des pecheurs au 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 up close.  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 they 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 commonsense, 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 import goal for this blog was to encourage you to start your own Tree Swallow project, even if that means 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 experence 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.  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 almost 40 years 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.

At the conclusion of each Tree Swallow nesting season I take a look at the overall performance of the Salmon Creek 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.

A Tree Swallow On The Absurdly Early Date Of 3/18!!!

So, 2012.  This has been an unusual year here at Salmon Creek in many respects.  It started with the entirely unexpected 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.

One Of Three Failed Feeder Experiments

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.  

Floaters Waiting For A Chance To Take A Box

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 boxes offered.

Floaters Converge On Box 12 Moments After It Has Been Put Up

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.

Females Quickly Learned To Use Dead Grasses Placed Below Boxes

Mute Swan feathers, which in past years were the feathers of choice for lining Tree Swallow nests, were very scarce in 2012, indicating 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.

Canada Goose Feathers Were Used Instead Of Mute Swan Feathers In Most Nests

Warm dry weather was the rule for the second half of the 2012 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.

The Littlest Nestling Was Fostered Into Box 10 And Supplemental Fed - It Fledged

There was one complete brood loss – in Box 14 all five nestings were found dead at about 4 or 5 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 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 five 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 2.  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 will continue banding in future years until I learn the large-scale banding study of Tree Swallows has concluded. 

A Potential Contributer To Tree Swallow Migration Research

As of this writing on 6/30, 70 of the 81 nestlings that hatched have fledged, and the last six in Box 2 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.

Flocking Up - Soon They'll Be Gone

A Few Tree Swallows Are Still Hanging Around, But Most Have Left

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 2 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 again 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 Last Active Box At Salmon Creek

I have to say Box 2 looks pretty isolated, but it is seldom alone, for passing juveniles are drawn to boxes containing nestlings as if by a magnet.  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.

The Late Nest In Box 2 Attracts Curious Juveniles

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 2 parents won’t have to search quite so hard for the 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 boxes for off-season storage.

Boxes Waiting To Be Washed And Disinfected

 Here are the Control Sheets for 6/28/12.  Click thumbnails for expanded views.

Control Sheet 1 For 6/28/12Control Sheet 2 For 6/28/12

Control Sheet 2 For 6/28/12

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 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.  However today, 6/25, it finally 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.

What A Wonderful Sight! A Well-Used Nest And No Dead Nestlings. Note How The Nestlings Tried To Defecate Away From The Nest Cup.

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 2, 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 died or deserted for unknown reasons, followed by desertion by the second 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 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 mature fully in the box it should be able to fly with 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. 

Two Recently-Fledged Juveniles In Flight. Note Short Wings And Faint Breast Bands.

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 did see this morning could be distinguished quite easily for 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 a noticeably more fluttery and mothlike.  I love to watch these young swallows wheel and bank, soar and dive, flap and glide.  At the risk of sounding antropomorphic 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.

Three Pesky Recently-Fledged Juveniles At An Active Nest

Here are the Control Sheets for 6/25/12.  Click thumbnails for expanded views.

Control Sheet 1 For 6/25/12

Control Sheet 2 For 6/25/12

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 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.  Now I don’t venture far into the field from the hedgerow, and I watch boxes through binoculars, which I seldom use until nestlings reach this stage.  And any photos I take now are shot from a distance and only at boxes on the grid’s edge whose adults I know aren’t overly excitable.  I apologize for the poor photo quality.

Feed Me!!!

A Typical Food Exchange To An Older Nestling

Control Sheet 1 For 6/23/12

    

Control Sheet 2 For 6/23/12

2012 is turning out to be a year 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% set in 2009.  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 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 supplemental feed 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.   

There Were So Many Little Guys This Year

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 past experience that persistent cold during incubation can correlate 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 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.

Two Of These Box 10 Nestlings Are Fosters From Other Boxes

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 of 4/26) 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.

Here are the Control Sheets for 6/22/12.  Click the thumbnails for expanded views.  

Control Sheet 1 For 6/22/12

Control Sheet 2 For 6/22/12

On an earlier post 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.  (If you missed this you can click here here to view it).  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.

I Know You’re A Male, But There’s No Way To Tell If You’re Second-Year or After-Second-Year

Why are SY males blue instead of a sub-adult brown like females?  I believe there are 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.

All We Can Say Is This Male Is After-Hatch Year (AHY)

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.  But if this SY male can attract females by appearing to be of “high quality” he can still become a father this year.  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 think high quality male SY Tree Swallows that look like older males are more likely to reproduce, so that 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.

An After-Hatch-Year (AHY) Male, Age Unknown, With An SY Female Here are the Control Sheets for 6/21/12.  Click thumbnails for expanded views.  Control Sheet 1 For 6/21/12Control Sheet 2 For 6/21/12

I Know Your Momma, But Who's Your Daddy?

These six young Tree Swallows are from the same nest and have 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 an explanation 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 cloaca under her tail to make cloacal contact 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 completely in charge of whether 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 to fertilize her eggs, and she doesn’t have to pick the male at her nest box.  You can view a short YouTube video clip of a female Tree Swallow rejecting a male by clicking here.

A Female Flips Her Tail Up, Preventing Copulation

Ornithologists have learned that some or even most of a female Tree Swallow’s brood may have different fathers through use of the same type of DNA profile tests that determine paternity in humans.  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 copulations with other males.  That’s right, your female bluebirds, cardinals, chickadees, etc., all show this behavior to varying degrees.

Um, Where've You Been?

The big question of course is why?  Why do so many female birds 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.  A related idea is that females “want” a variety of different genetic combinations in their offspring, because this may result in better odds of her having some descendents which able 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 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.   

Here are the Control Sheets for 6/19/12.  Click the thumbnails for expanded views.

Control Sheet 1 For 6/19/12

Control Sheet 2 For 6/19/12

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!

A Fecal Sac - You Get To Wear A Lot Of These When Banding Nestlings

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.  Banding nestlings would be easy if they weren’t such squirmy little critters and their legs weren’t so short.

Banding A Semi-Cooperative Nestling

But there is one extremely important thing that banders must know about Tree Swallow nestlings.  They can 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 forbidding 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 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 probably be forced to intervene to save the nestlings’ lives, whatever their age.  (Information on emergency mite control can be found by clicking here). 

The Wing Of A 12 Day Old Nestling. If A Nestling Has Wing Feathers More Erupted Than This Don't Disturb It's Nest!

Will these banded nestlings return to Salmon Creek next year?  If they were adults I would expect to see about 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 SY’s will find my nest boxes already claimed by older adults.  So the nestlings, now SY’s, 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 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 after 2007 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 happened a minimum of five times.  The Box 4 female was banded as a nestling in 2007, so this 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 major coordinated effort to better understand the migration routes, stopover roosts and wintering ground 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.

Will You Turn Up In A Researcher's Mist Net In Louisiana or Florida?

Here are the Control Sheets For 6/17/12.  Click the thumbnails for expanded views.

Control Sheet 1 For 6/17/12

Control Sheet 2 For 6/17/12

In The Beginning - A Newly Hatched Tree Swallow

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 audable 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 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 ability differences may effect nestling growth.  Parasites can occasionally depress growth rates.  Genetic variables may come into play.  And to further complicate matteres 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 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.

Note The Dark Feather Tracts On The Back, Tail And Wings Of this 4 Day Old

Between about day 5 and day 7 eye slits open.

A Smallish 7 Day Old Nestling From Box 10 With Eyes Opening

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.

Both Flight And Contour Feather Sheaths Are Sprouting On this 7 Day Old From Box 7

As feathers erupt out from the ends of their 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.

Feathers Are Erupting From Sheaths All Over This 9 Day Nestling From Box 4

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.

A 12 Day Old Nestling Looking Rather Birdlike As It "Hides"

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 they will die.  So any observations I make after day 12 will 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 a shiny new band.

Here are the Control Sheets For 6/15/12.  Click the thumbnails for expanded views.

Control Sheet 1 For 6/15/12

Control Sheet 2 For 6/15/12

What A Mouthful! A Tree Swallow With A Bolus Of Insects

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 hand-feed 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 between about four days and 12 days during prolonged severe weather, just to get them through 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.

This 4 Day-Old From Box 13 Is As Small As I Can Feed

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: http://www.sialis.org/feeder.htm).

Keeping Mealworms In Flour And Bran Flakes With Potato For Moisture

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.

Bringing A Nestling To Be Fed

Gently Opening The Mouth

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. 

Inserting The Mealworm Headfirst

I like to give nestlings a minute or so 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 it out.  A nestling is never forced to eat if it clearly doesn’t want to. 

Down It Goes

Almost Gone

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 the next box with a needy nestling.

Mmmm! Yummy!

Once I’ve completed a round of feedings I’ll do something else for an hour or so, then 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.

Here are the Control Sheets for 6/13/12.  Click thumbnails for expanded views.

Control Sheet 1 For 6/13/12

Control Sheet 2 For 6/13/12

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 have almost caught up – their parents must be excellent providers – but those in Boxes 7, 10 and 13 had not 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.

Box 7 Has A Brood Reduction Nestling

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 of 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 another 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.

The Temporary Blue Mark Will Identify This Fostered Nestling

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 Box 7 five nestlings hatched on 6/5 and one on 6/6, with the result seen in the first photo of this post.  

Box 10 Had One Large, Three Medium, And One Small Nestling On 6/9/12

My plan was to foster 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. 

The New Box 10 Brood Includes A Foster From Box 7 In The Middle

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.

Control Sheet 1 For 6/11/12

Control Sheet 2 For 6/11/12

This Egg Finally Hatched A Day After The Other Four

Why don’t eggs always hatch the same day to avoid this problem?  The hatching pattern depends on the incubation pattern of the 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 the 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 have excess nutrients within her in a good year, so even though her body says it’s time to incubate, maybe she’ll go ahead and incubate but use her surplus nutrients to produce an “extra” egg the next day.  Or, some individual females could simply be genetically “programed” 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 in trouble.

Can You Spot The "Brood Reduction Nestling"?

So after carefully scrutinizing the Tree Swallow hatch at Salmon Creek in 2012, 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 nestmates.  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 blog posts.

Here are the Control Sheets for 6/9/12.  Click the thumbnails for expanded views.

Control Sheet 1 For 6/9/12

Control Sheet 2 For 6/9/12

It is 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 nestlings, so 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 had 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 haven’t banded since 2007 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 large-scale 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 in 2012.

A Simple Tape-Hinged Barrier For Box Trapping

I don’t use mist nets to capture Tree Swallows.  Instead I use a procedure I learned from 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.  The trap consists of a simple plastic barrier, attached temporarily inside a box using a masking tape hinge, and propped up with a piece of dried plant stem.

Barrier Propped Up With A Stem, Ready To Fall Into Place

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.

The Barrier Has Fallen, Trapping The Swallow Inside

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 I apply the band, measure wing chord length, and take the bird’s weight.  Each bird’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.

A Band Is Applied Using Special Pliers

Measuring The Wing Chord With A Wing Rule

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.

Checking For A Brood Patch Or Cloacal Protruberance

Today is just the start of banding operations here.  By the end of the 2012 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.

Here are the Control Sheets for 6/7/12.  Click the thumbnails for expanded views.

Control Sheet 1 For 6/7/12

Control Sheet 2 For 6/7/12

In The Last Nest, Box 14, Egg Laying Is Now Complete

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 somewhat 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. 

The First To Hatch In Box 6 Pushes Its Shell Halves Apart

This morning, 6/5, it seemed hatching was ocurring 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. 

The First Hatched In Box 10 Is Ready For Food

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, etc. 

Three Hatched And Four To Go In Box 5

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 have lower rates of cooling when the females are away.  The feathers may also help 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.

Well-Feathered Nests Seem To Help Keep Nestlings Warm

Here are the Control Sheets for 6/5/12.  Click the thumbnails for expanded views.

Control Sheet 1 For 6/5/12

Control Sheet 2 For 6/5/12

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 foraging for 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.

A Male Checks A Box During The Incubation Period

Today, 6/3, hatch began.  As of 2:00 PM fifteen eggs had hatched in three boxes.  In Box 4 all six eggs have hatched, and 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 be on.

Five Out Of Six Eggs Have Hatched In Box 3 So Far

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” 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 below is.

A Just-Hatched Nestling's Down Is Damp

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 dawn to 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. 

Here are the Control Sheets for 6/3/12.  Click the thumbnails for expanded views.

Control Sheet 1 For 6/3/12

Control Sheet 2 For 6/3/12

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.

Licensed Banders At Work At The Braddock Bay Bird Observatory's Kaiser - Manitou Beach Banding Station

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.

A Mourning Warbler Gets A Band

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 species’ migration patterns and geographic ranges, population changes, and identification issues.

Measuring The Wing Chord

Using Calipers To Measure A Tarsus

In addition to routine banding activities the Observatory collaborates onsite with professional ornithologists and their students, investigating such topics as inflight 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 if you check Control Sheet 1 below you’ll see the incubation period is 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.

A String Of 100 Size #1 Bands

For more information on the Braddock Bay Bird Observatory see: http://braddockbaybirdobservatory.wordpress.com/.

Here are the Control Sheets for 6/2/12.  Click the thumbnails for expanded views.

Control Sheet 1 For 6/2/12

Control Sheet 2 For 6/2/12

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.

A Male And A Second-Year (SY) Female Tree Swallow

Many bird species have subadult plumages, in which younger individuals look different.  In these species individuals must molt through one or more different plumages as they age before finally attaining the 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 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?  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 too many aggressive takeovers by SY females to buy the notion that their brown plumage signals subordinance.  And I’ve witnessed too many resident females attack 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 the ASY class claim most available nest sites.  When the SY swallows, both males and females, do arrive on the breeding grounds they can either risk trying to take a nest site from older more experienced birds or, being unable to outcompete the residents, they can join the weaker, “lower-quality” ASY’s and float, prospecting and hoping for a nest site vacancy to occur.  A very few, super high-quality SY’s might be able to take over early nests, but most SY’s 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 SY’s?  If I were a male Tree Swallow with a nest site, intent on passing my genes on to future generations, I would prefer to mate with a high-quality female.  But how to identify one?  At this later time the pool of potential mates includes some blue ASY females and almost all the SY females.  By definition the available ASY female floaters 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 ASY’s available at this time.  And as a male Tree Swallow I can tell the age-classes apart - ASY female floaters are blue, SY’s 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.

There’s Nothing Subordinant About This SY Female As She Defeats An ASY Female For Late Box 11

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.  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!

This Box Is Mine!

If you’re interested in a much more detailed explanation of this ridiculous idea contact me and I’ll send you a hardcopy.

Here are the Control Sheets for 5/31/12.  Click the thumbnails for expanded views.

Control Sheet 1 For 5/31/12

Control Sheet 2 For 5/31/12

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; they’re just covered over.

Where’d The Eggs Go?

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.  Unfortunately, laying “skips” can also hint at 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 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.

A New, Very Small Female Has Bonded With The Box 2 Male

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, 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 in 2012.  Adding boxes had satisfied most of the floating population, and in most boxes eggs were laid and are being quietly incubated now with no strife worth mentioning.  However, there’s 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 now house House Sparrows, who may have driven out Tree Swallows I’d seen investigating.

For record keeping purposes I am calling this second nesting attempt 2A, as you may have seen on Control Sheet 2.  You may also have noticed that the new 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. 

Here are the Control Sheets for 5/29.  Click the thumbnails for expanded views.

Control Sheet 1 For 5/29/12

Control Sheet 2 For 5/29/12

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!

Tree Swallows Are Using This Tiny Box

Years ago someone, somewhere had the bright idea that House Sparrows, a non-native scourge 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 Wood Duck boxes down to tiny decorative boxes never meant for actual bird nesting.  The swallows don’t appear to have any “judgement” 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 these small “sparrow deterring” bluebird boxes, which in reality are miserable little death traps.

What Will Life Be Like For Young Swallows In This Little Box?

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 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.  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 trouble.  You’ll be trampled and become soiled with feces.  You’ll be smothered by your nestmates’ warm bodies during hot spells.  You won’t be able to position yourself to reach food your parents bring.  You’ll lag behind the stronger ones 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 nestmates 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 picture below 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?

Comparing Nest Box Floor Sizes

Do you understand why I’m angry at those bluebird hobbyists, clubs and bird supply stores that continue to advocate 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: http://www.treeswallowprojects.com/buildbox.html

For a Bluebird versus Tree Swallow “reality check” see: http://www.treeswallowprojects.com/tresvsbb.html

Here are the Control Sheets for 5/27/12.  Click the thumbnails for expanded views.

If you check the Control Sheets at the bottom of this post you’ll see almost all the female Tree Swallows at Salmon Creek have finished egg laying and are now incubating.  But when incubating they spend the nights in their boxes, which puts them 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 prevents most predation, but I prefer to go it one further and equip each of my boxes with predator guards.  The trouble for most people, myself included, is commercial guards are prohibitively expensive, but after raccoons cleaned out most of my boxes one night many 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.

A Cheap And Simple Predator Guard

I remove the ends from large juice cans (Hi-C, V-8, etc.) and cut 7-8 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.

A Juice Can Guard

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.

A Grease Band Below The Guard Adds Protection And Keeps Out Ants

Raccoons Can Climb Almost Any Pole

Control Sheet 1 For 5/26/12

Control Sheet 2 For 5/26/12