As storms rolled through overnight, I assumed I might find a casualty this morning. There were two: a completely rain-soaked female Indigo Bunting in the southwestern alcove and a completely dry and fluffy Mourning Warbler at the south entrance under the rain protection provided by the portico’s overhanging roof. The latter was an AHY male with fat = 3.
Since Monday night, we seem to have received at least 5 inches of rain here in Stillwater. That’s great as I’ve been lamenting the lack of even clouds for a few weeks. The system that brought the rain might have kept birds bottled up to our north because once it cleared last night (Wed.) there was one heck of a flight.
Of course, attempts to correlate window collision mortality with big radar echoes of migrating birds are fraught with confirmation bias. There are plenty of big flights that result in no dead birds on my rounds, and I’m a lot more likely to check “last night’s radar” on a morning when I find multiple casualties. Today was one of those days.
I walked to the Noble Research Center on a route that took me past the long row of windows on the southern side of the Food and Agricultural Products Building, aka, FAPC. This is just across a parking lot from the NRC and I’ve made several incidental finds there. Today, these “bonus birds” numbered three: an Ovenbird, a Common Yellowthroat (collected) and, around the corner, a female Indigo Bunting that had been there for at least a few days. So before I even made it to the NRC, I encountered 3 window-killed birds.
The yellowthroat was an apparent AHY-male, with fat = 2 and weighing in at 12 g.
At the NRC was another surprise. Surprisingly, after all these years and considering how common these birds are as migrants and wintering residents, I found the project’s first Savannah Sparrow, in the northwest alcove.
There was also a trapped Common Yellowthroat at the main north entrance and another Savannah sparrow flitting around – through not trapped – just west of the southern portico entrance. The Savannah Sparrow was AHY-U, weighing 18g with a fat score = 2.
I was out of town from 21–30 June and no surveys were run during that time. On June 30th, however, I heard from Dawn Brown and Corey Riding that there were three casualties at the southwestern alcove of the Noble Research Center: a badly decayed Northern Parula (adult male), a female Ruby-throated Hummingbird, and a female (with brood patch!) Indigo Bunting. It’s possible that the bunting came in on the 30th, but the others were clearly killed prior to that date. (Photos by Dawn Brown.) This is officially the first Northern Parula found on the project.
With special guest stars James O’Connell and David Mallen, today’s survey turned up a male Indigo Bunting and a trapped Yellow Warbler at the main north entrance. (No photo of the warbler; it was a male.)
Let’s take a closer look at that Indigo Bunting:
The multiple obvious molt limits on this bird illustrate two generations of feathers on the same individual, some of which grew in last summer and some which have come in quite recently. This confirms the age of the bird as second year (SY).
Sad to think that this spectacular specimen of an ASY male (fat = 2) Indigo Bunting safely crossed the Gulf of Mexico a few days ago but could not safely navigate the Noble Research Center.
Indigo Buntings, of course, have no blue pigment. Blue is produced by birds through light reflectance – it’s structural color, not pigment.
You might think, then, that Indigo Buntings would look really cool in UV light. They don’t, unless you think charcoal looks cool!
The photos illustrate how obvious it is to find many of the carcasses at the Noble Research Center. Today it was an Indigo Bunting in the southeast alcove.
This was a hatch-year bird and probably a male owing to the faint bluish tinge in the wings and tail. Were those blushes of color resigned to the upper tail coverts, female would be a bit more likely. Fat = 0 on this bird.
The SY male Indigo Bunting I found yesterday has been moved, but not removed:
Presumably, this was a human moving the carcass from in front of the entrance to a more secluded location.
Today I found a Red-eyed Vireo in the southwestern alcove and an Indigo Bunting at the main north entrance.
The Indigo Bunting was a second-year male with zero fat and an impressive contrast of old and new feathers. I left him in place for a removal trial. The Red-eyed Vireo, an ASY female with a brood patch and no fat, is the first vireo I’ve ever recovered as a window-kill from the NRC.
No sign of any new casualties today, and no sign of the Indigo Bunting that lasted for 6 days.
Science can be messy, especially when the subjects are living beings outside of a laboratory setting.
Here’s the latest illustration of this principle: If you had asked me last week if Indigo Bunting was a species that commonly shows up in my surveys for window-killed birds at Oklahoma State University’s Noble Research Center in Stillwater, I would have responded that I’ve found a few, but not an unusually high number of them. Indigo Bunting was the 10th most frequently recorded species on my surveys. From August 20, 2009 to May 4, 2014, I had only found 4 individuals of this species. So in nearly 5 years I had found 4. I would have been pretty confident in those 5 years of data, too. After all, that’s the value of long term ecological research. It provides a greater opportunity than in short term studies to identify patterns in data, including unusual events.
Speaking of unusual events, we’re in one now: Since, May 4th, I’ve found FIVE Indigo Buntings dead at the NRC. In five years I found 4 individuals; in the past week I found 5. Oh, and all 5 have been females. Today’s was an ASY female with fat = 0.
In other news, the Clay-colored Sparrow is now gone without a trace (it lasted 5 days), but the Indigo Bunting I left out yesterday has not been touched.
The onslaught continues.
This morning, the Clay-colored Sparrow was in place and had not been touched. I was happy to not see a Gray Catbird, Painted Bunting, or Wilson’s Warbler limp on the ground, which means that I was at least successful yesterday in getting those birds away from the building.
There were, however, three new casualties today. First, there were two female Indigo Buntings, one in the southeast alcove and one along the north facing wall. I collected one and left the other in situ. The one I collected was an ASY female with fat = 2.
Female Indigo Bunting #1, collected:
Female Indigo Bunting #2, left in situ:
In the southwestern alcove, I found this gorgeous ASY male Yellow Warbler. This one had no visible fat, making me wonder if he exhausted himself as a trapped bird rather than dying suddenly from impact trauma.
Here they are together prior to internment in my freezer:
Casualties have seemed remarkably low this spring. As a conservationist I’m grateful for that, because fewer dead birds is a good thing. As a scientist, it bothers me a bit, because every time I get complacent enough to think I might understand mortality patterns of avian window collisions at the Noble Research Center, the data throw me a curve ball. In truth, the spring of 2013 was a bit like this too: strangely low mortality during April when it seemed like the bulk of migrants were passing through, but then a flurry of casualties through May – and into June – when out birding it seemed like migration was really at an ebb.
It’s easy as well to fall prey to confirmation bias in thinking that a lot of birds passing through correlates with peaks of mortality. Often I have posted images of bird migration captured on radar after finding a bird or two dead at a window so that I can exclaim “Aha! No wonder we had casualties last night – check out the flight!” That correlation would only matter, however, if the great many heavy flights captured on radar were always associated with casualties I find. I don’t post those radar images for days when I collect negative data. All that said, it’s no wonder we had casualties last night – check out the flight!
This morning I had the good fortune to collect data on the misfortune of these two, female Indigo Buntings. Beginning birders take note of these small, drab, brown “sparrows” you might be seeing all summer long, because they rarely sport enough indigo to rely on color for their identification.
I aged both to after second year based on primary covert shape, and both were carrying some fat but not a lot. I coded them = 1. Neither had brood patches. It can be tempting to picture them traveling together last night, perhaps in a small flock of Indigo Buntings, but they ended up on different sides of the building. Also, the top bird in the photos was pretty stiff – as if she had hit several hours before the bird in the bottom, who was limp and seemed just barely lifeless in the hand. Here is where they ended up:
Like so many others, they were oddly placed for spring migrants: Why on the north and west sides of a building when presumably they had come from the south, and likely southeast? I can only picture some kind of local movements that are multidirectional as birds are finding safe spots to put down for the day, and the funnel-like shapes presented by the Noble Research Center draw birds in and, unfortunately more often than not, to their doom.
No casualties today, but yesterday a student brought my attention to a plastic container apparently just inside one of the doors at the NRC that contained a dead Indigo Bunting. She said she had seen it there for “weeks”; I indicated that if it was really an Indigo Bunting it more likely had been in place for months.
The student procured the container for me: Sure enough, it was a plastic, lidded container in which it appears someone had used a knife to cut “air holes”. Inside was a near immaculate condition male Indigo Bunting, except for the fact that when I opened the lid the stench was close to the worst I had ever experienced from a little bird.
I don’t know what to make of this. Had someone found the bird alive, put it in a box to help it recover from being stunned from a window strike, and then forgot that it was there? Did someone find the bird and leave it there for me to collect? It certainly is a mystery. I cannot even say for sure it was a casualty from the NRC or even from a building on campus. Maybe someone found it at their home and brought it in hoping I would find it? However you slice it, I consider it to be an example of gross negligence, and I just hope the poor little guy didn’t suffer too badly from its ham-handed treatment.
At first glance, it looked like these two “sparrows” were flying together and hit the same window. A closer inspection revealed that while they might have ended up in the same spot, they arrived independently.
Today I found a female Indigo Bunting, apparently AHY. The insects had already gotten to her head – that’s the black “patch” she shows above her eye. This indicates to me that she was actually a casualty from yesterday morning, the 7th. I moved her to the side and will monitor the progress of her removal. (The cardinal remains evident to me.)
A bit closer to the window was this HY Grasshopper Sparrow. This bird was in excellent condition (fat = 2) in life – indicating that it was migrating – and its carcass was much fresher than that of the Indigo Bunting, indicating that it died more recently.
This bird I collected and put on ice. It will be interesting to learn eventually where this bird was born and where it might have been headed so early in the “fall”.
I found an SY female Indigo Bunting this morning on the north side of the NRC. She allowed me to pick her up, squawking about that a bit, but I’m not optimistic about her recovery. Generally, if a wild bird with no other obvious external injury allows me to pick it up, I assume it’s got things wrong on the inside that are irreparable.
I moved her to a secluded spot in dense vegetation by Cordell Hall with a clear sightline to the north, but I will count her as a mortality given her condition.