30 September 2013 – Lincoln’s Sparrow and trapped Yellow-breasted Chat

Another Lincoln’s Sparrow this morning, this time at the south windows on a north wind.  This bird had little fat, but otherwise looked to be in great shape.  On the north side, there was a very lively Yellow-breasted Chat.  Near as I can tell, the chat got away apparently unscathed.

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22 September 2013 – Yellow Warbler

This hatch year female Yellow Warbler was cut short on her first southbound migration.  Fat = 2. She was a classic “confusing fall warbler” with an olive back and yellow breast, but the clincher for her identification was the pattern of yellow inner vanes on her tail feathers.  This is unique to Yellow Warbler among the North American parulids.

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21 September 2013 – Clay-colored Sparrow and trapped Common Yellowthroat

The night before last, we had our first real cold front of autumn push through, pushing overnight lows down to the 50s for the first time in months.  I expected that yesterday would have been a big flight that would result in window collisions, but last night seems to have ushered in a bigger wave of migrants.  I found two at the south face of the Noble Research Center this morning (providing additional evidence that the direction of the prevailing wind has little to do with where on the building birds will end up).

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The first was this beautiful Clay-colored Sparrow (fat  = 2):

 

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Not far away was this Common Yellowthroat.  She was very much alive, and I was happy to see her fly away strongly when I shooed her away from the building.

This bird was an ID challenge:  She was very pale on the throat, breast, and belly, but her yellow undertail coverts were quite obvious.  That pattern, and the fact that she was pumping her tail a bit, had me thinking she might have been a Palm Warbler.  Her pale legs and the lack of white on the tail tips ruled out Palm Warbler, as did her lack of other plumage details that might have strengthened the link.  Instead, she looks to me like a hatch year, female Common Yellowthroat, but from the “Interior West” according to Sibley: those are the yellowthroats that can lack yellow throats, unlike the eastern subspecies that should show a bright yellow throat in all plumages.

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15 September 2013 – Empidonax flycatcher, Traill’s type

On Sunday morning, September 15th 2013, I encountered the 47th species and 144th casualty on the study.  The find was unusual in that the poor bird was not quite dead and that, despite holding it in my hand, I am unable to say for sure what it was.

To begin, the bird was in pretty bad shape when I first found it, listing to one side and unable to perch anywhere but prone on the ground.  That said, it was alert and aggressive, and it flew from me twice before I could get a hand on it.  Its flight, however, was weak and out of control, and it was exhausting itself to get away from me.  This was a bird right on the edge: my inner intellectual monologue told me to euthanize it but my inner emotional monologue kept hoping for its fighting spirit to save the day.  I held it for some time, carried it south of the Library where it had clear flight lines in all four directions, and even carried water to it from the OSU fountain, gently dipping its snapping beak into the tiny puddle in my hand.

In the end I placed it on the ground in a juniper hedge along the quad.  It was alive when I left, but still listing to one side.  Without my intervention it would have died; with my intervention it had a tiny chance of survival.  I am counting it as a window casualty rather than a trapped bird.

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So what was it?

My first concern was that it was the Eastern Wood-Pewee from a few days ago, still hanging around and slowly wearing itself out.  This bird’s smaller size, greener back, and more bold wingbars convinced me instead that I had an Empidonax flycatcher.  Which one?  I’m guessing a Traill’s type, and probably Willow.

“Trapped” birds – how to count collision victims that survive the initial impact?

<This is an update to a post composed in 2013. We know a bit more now about injuries sustained by birds from window collisions. No, their necks still aren’t breaking and yes there still is a lot of beak damage. Brain hemorrhage can be difficult to determine from normal pooling of blood that can happen anytime a bird carcass lays on its back, however, so we might be overestimating brain injury incidence. Internal injuries, especially fractures of the coracoid (avian bone joining sternum to shoulder) that puncture air sacs, might actually be more common than generally appreciated. Stay tuned for updates from ongoing research in this area.

More important, wildlife rehabilitators have made strides in the treatment of birds that have collided with windows, including those that have suffered a traumatic brain injury. Thus it’s a good idea to keep handy information on your nearest rehabber and specifically seek their advice in advance for best practices in giving birds that survive an initial collision the best chance to make a complete recovery.

Here in Stillwater, OK we have two great options: Nature’s Vein Wildlife Rescue and Education (405-665-0091) and the OSU Vet Hospital:

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Now then, back to that old post . . .>

 

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Black-throated Blue Warbler in passage on a clear night, by Tim O’Connell

Several things can happen when a bird approaches a building.  Some birds approach and, seeing either a reflection of the grass, trees, and sky behind them or the grass, trees, and sky on the other side of a visual pass-through, simply collide with the window at whatever speed they were flying.  Many of these birds (Dan Klem estimates about 50% of them) will suffer a severe injury and die immediately.  Others might be stunned, knocked out, or otherwise impaired to the point that they cannot fly.  Of these that don’t die immediately, some will recover fully and some will die some time later, either because they are easy pickings for a neighborhood cat while in their dazed state or because they’ve suffered too much brain damage for “time” to repair their wounds.  Some birds will be dazed from the initial collision and able to fly to some more protected perch nearby where they will either recover on their own or ultimately die, but at least they are better protected from predators if they can make it to the relative safety of a nearby tree. Klem estimates that 50% of those that die from windows succumb to their injuries sometime after they leave the site of the collision.

I find these injured-but-not-dead-birds rather frequently: 56 individuals since I started paying attention during the fall of 2009.  As of August 2012, I’ve also been recording the location I first encountered each of these live birds.  Some of them look pretty rough when I find them, but if when I grab the bird it makes a fuss and tries to escape from me, I consider that it’s got a fighting chance to recover from whatever injury was so severe that it allowed me to catch it by hand.  These feisty birds I carry away from the building and place in some dense shrubs or low branches.  This way, the bird is out of the direct sun and has some better cover from predators while it regains its wits.  If the bird is, when I leave it, alert and able to perch strongly, I usually will not count it as a “casualty”; I’ll assume that it’s one of the ones that would have survived its ordeal.

Some birds, however, are neither feisty or alert.  Their bodies droop, their eyelids sag, they might be panting heavily, they can neither hold onto a perch or stand up straight in the palm of my hand.  The prognosis for recovery is very poor for these birds, and I have euthanized 3 or 4 of them in this condition, and counted them as casualties.

There is another category, however.  Some birds are found in fine physical condition:  active, volant, and apparently not dazed in the least.  They are, however, out of place, like the Eastern Wood-Pewee I found this morning perched on the ground, on a sidewalk, in an exterior alcove of the Noble Research Center.  These birds are “trapped” in the sense that they are in inappropriate habitat and, like a classic funnel trap, for some reason unable to figure out that they simply need to fly back the way they came for 100 m or so so they can clearly see how to fly around or over the building.  Instead, they might spend hours flying back and forth against the back wall of the alcove.  In this way, I suspect that some birds die from the stress and exhaustion of this experience, and that they might never actually strike the window with enough force to cause injury.  It is the shape of the building as much as its windows that makes it deadly for migrant songbirds. This could be one reason that the dead birds that I find are so often in immaculate shape: they are perhaps dying from cardiac arrest or exhaustion as opposed to trauma from collision.

So I consider trapped birds to be either of the following:

* a live bird that I am able to catch and move to a secluded location where, based on my assessment of its condition, I judge that it can survive the experience,

* a live bird that I am able to “shoo” or herd away from the building.

13 September 2013: trapped Eastern Wood-Pewee and Mourning Warbler

I had two trapped birds at the Noble Research Center this morning, both of which presented identification challenges because they were in good enough shape that I never got to examine them closely.  I first found what turned out to be a wood-pewee (and I’m assuming it’s Eastern) at the northeast alcove and then found a warbler I’ve identified as Mourning at the northwest alcove.  I was able to steer both birds away from the building so I am hoping that I won’t find them dead there tomorrow morning.

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Here’s the wood-pewee.  When I first came upon it, it was sitting on the ground, its long, low shape and attenuated bill had me momentarily thinking it was a swallow.  As I approached (within just a few feet) it was clear that I actually had a flycatcher, but it wasn’t until it flushed to perch on a nearby railing that I figured out that it wasn’t an Eastern Phoebe.

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This bird was intermediate in size between a phoebe and and Empidonax flycatcher.  It lacked the white throat of an Eastern Phoebe, it showed a bi-colored bill, and it did not wag its tail.  Relative to Empidonax flycatchers, this bird was larger and lankier, with a long primary projection, little to no greenish cast on the upperparts, no obvious eyering, and a dusky grayish vest.  All signs point to it being a wood-pewee, and I can only assume it’s Eastern as I wouldn’t be able to distinguish it from an extralimital Western in a photograph.  The buffy wingbars suggest a hatch-year bird. This is the first wood-pewee on the project, and here’s where Easterns have been reported this month:

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The Mourning Warbler on the northwest side of the Noble Research Center was also in good enough condition to fly off on its own, so I was left with my crude photographs to make the identification.  At first blush, the olive-green upperparts, yellow breast and throat, and grayish head suggested Nashville Warbler.  The structure didn’t fit well, however.  The bill wasn’t narrow enough for Nashville, and the pale lower mandible didn’t fit either.  The eye-ring seemed thin, and broken, unlike the bold, complete eyering on a Nashville.  The feet were big and pale, as opposed to a Nashville’s small, blackish feet.  The yellow throat pegged the bird as hatch-year, but I’m reluctant to call the sex.

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3 September 2013 – Wilson’s Warbler

Hatch-year female; fat  = 2.

We had a big flight last night, on the heels of a decent cold front.  Sadly, this Wilson’s Warbler failed in her first attempt to make it to Mexico for the winter.

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2 September 2013 – bonus Mourning Warbler

No casualties at the Noble Research Center this morning, but I found this bonus Mourning Warbler on the south side of the Food and Ag Products Center.

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This was a hatch year bird, and probably a female.  She was in prime shape for migration, with fat = 2.  No Mourning Warbler should end up stiff on a sidewalk in Oklahoma.  Here’s where these birds are supposed to be in the first two days of September:

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