A storm blew through yesterday that dumped 3″ of rain on central OK. Evidently caught up in that mess was this Red-eyed Vireo in the southwestern alcove.
Though they might have come in yesterday (when I didn’t check), there were two birds in the southwestern alcove today: a Tennessee Warbler (AHY-U, fat = 2) and a Painted Bunting (SY-U <probably female>, fat = 2).
There was also a bonus at the Food and Ag Products Center: a window-killed Yellow-billed Cuckoo and a trapped Black-and-white Warbler. The warbler flew off fine as I approached.
The first casualty of 2018 – and the 334th on the project – was an AHY (after hatch year, i.e., adult) male Northern Cardinal at the southeast alcove. He was probably an ASY (after second year, i.e., definitively hatched prior to 2017), but one cannot be entirely sure because cardinals occasionally undergo a complete molt in preparation for their first breeding season, and it’s not possible to age them any more specifically than AHY based on plumage characters (i.e., molt limits) alone.
One thing is pretty obvious for this cardinal: The trauma at the tip of its bill indicates a significant collision took place. Evidently, he was attempting to fly through the pass-through illusion to the southwestern alcove.
I left the bird in place (actually a few meters off to the side so it wouldn’t get stepped on by traffic through that entrance) and it was present on the 17th and 18th, but gone on the 19th.
I’ve been behind with stacks of papers to grade, and they’ve kept me from keeping up as often as I’d prefer. During the period from October 7–18, I conducted 8 surveys, skipping Oct. 8, 14, and 15. The data from these last 11 days look a bit like this:
- Oct. 7: HOWR
- Oct. 9: no casualties
- Oct. 10: no casualties
- Oct. 11: LISP
- Oct. 12: TUTI
- Oct. 13: no casualties
- Oct. 16: OCWA, SOSP, LISP, and NAWA
- Oct. 17: no casualties
- Oct. 18: no casualties
Just past mid-October, and we are crushing the annual mortality count right now with 55 dead birds.
Oct. 7 – I found just the third House Wren on the project. This one ended up on a warm air outflow grate from the air conditioning unit and was quickly desiccated.
Oct. 11 – I collected this Lincoln’s Sparrow from the south portico.
Oct. 12 – This Tufted Titmouse was a surprise in the southwestern alcove.
Oct. 16 – This was not a good day for migrants. I found an Orange-crowned Warbler at the northeast alcove, a Song Sparrow at the south portico, and a Lincoln’s Sparrow at the southwestern alcove. Shortly after completing my survey, a Nashville Warbler was turned in from a collision in the southwestern alcove.
Hummingbirds have been takin’ it in the shorts of late . . .
But what’s with the fractional hummingbird reference above? Well, “scavenging” and “removal” are not necessarily the same thing. Often I find the remains of a bird that has been scavenged, but there’s enough left behind that I am able to detect that a casualty has occurred. Those remnants – let’s say a pile of flight feathers left behind by a scavenging cat – can last in place for many weeks. Each time I survey for casualties I’m greeted at that spot with the information that a bird died there (or at least somewhere nearby) even though all the edible bits are long gone. We should be clear that scavenging isn’t the important rate to help us better estimate detection of window-killed birds, removal is. It’s only when every piece of that carcass is gone that I’m unable to detect the evidence of a casualty.
We see this played out all the time with hummingbirds. For some reason, the ants seem to get to the hummingbirds more quickly than they get to other birds. (I have some hypotheses about this, e.g., that hummingbirds are more often flying in daylight and might have lain in place longer than the night-flying warbler and sparrow migrants.) The result is that hummingbird carcasses are rarely in pristine shape when I find them, but they are still there.
Check out hummingbird #1 this morning from the southeast alcove. First, look how obvious it is to detect the carcass even from ~20m away. Up close, note that a good bit of her face has already been carted away, one ant-mandible-sized piece at a time.
This next one (or 0.33 of one) from the southwest alcove will put your observational skills to the test:
See it yet?
Oh, that explains it!
In this case, there’s a pre-scavenged hummingbird (likely also AHY-F Ruby-throated) that is represented by its tail only. But it’s still detectable and largely identifiable.
(UPDATE 10 AUGUST 2017: Today I found a head and wing near where I found the tail on Aug. 9. First, this looks much more likely as a HY-M than an AHY-F. Also, literal scavenging seems less likely. I suspect more that the carcass was chopped up by a lawnmower.)