Six-month summary: July–December 2010

Here is just a quick summary of casualties at the Noble Research Center from July through December 2010:

Very fat Mourning Warbler that never made it to the wintering grounds.

I detected 25 individuals of at least 16 species among the casualties. The complete list:

grasshopper sparrow – 4
ruby-throated hummingbird – 2
mourning warbler – 2
song sparrow – 2
Lincoln’s sparrow – 2
unidentified passerine (1 warbler, 1 sparrow) – 2
black-and-white warbler – 1
Carolina wren – 1
mourning dove (juv) – 1
least flycatcher – 1
common yellowthroat – 1
black-throated green warbler – 1
brown thrasher – 1
house wren – 1
red-breasted nuthatch – 1
white-throated sparrow – 1
field sparrow – 1

Because I was able to get to the NRC earlier each day during autumn than practical in 2009, I encountered more individuals that were stunned and “trapped” by the building for some time period without obvious mortal injury. Most of these birds are presumed to have eventually moved on, but it is quite likely that the house wren and one of the Lincoln’s sparrows on the “stunned” list were unsuccessful in their respective bids to escape from the confusion of the NRC, and are listed above. The bat represents the first mammalian “capture” by the NRC:

Lincoln’s sparrow – 5 (4 in one flock)
house wren – 1
common yellowthroat – 1
Nashville warbler – 1
grasshopper sparrow – 1
dark-eyed junco – 1

It’s dark when migrants like this Lincoln’s sparrow drop out of the sky and try to find a good spot in which to rest for the day. I’m beginning to think that most collisions are occurring in that last hour before sunrise.

September 2010 summary

It looks like Sep. 1 is the only day I did not check for casualties this month. Here’s what I found on the days I did check:

2 Mourning Warblers
1 unidentified warbler
1 Least Flycatcher
1 Common Yellowthroat
1 Black-throated Green Warbler
1 Ruby-throated Hummingbird
1 Brown Thrasher

7 Sep. 2010 – Least Flycatcher and Common Yellowthroat

I found two unlucky young migrants this morning, a Common Yellowthroat and a Least Flycatcher. Both were hatch year birds with fat scores of 1. The yellowthroat was a male; the sex of the flycatcher is unknown.

While the yellowthroat was easy to identify, the still-warm Empidonax flycatcher presented a challenge. I used Sibley’s Guide to Birds and Kaufman’s Advanced Birding to nail it down.

The bird is small (total length ~ 132 mm or 5.33″) and it has a broad yellow-orange bill with a diffuse dusky tip. It has complete eyerings that do not flare behind the eye. The primary projection is relatively short (0.18 the length of the wing chord). The belly and undertail coverts are a creamy yellowish-white – this area is separated from the grayish-white throat by the olive-gray breast band. All of these features are congruous with Least Flycatcher. The buffy wing bars and tertial edges confirm it as an immature bird. Because this is a new species for the NRC monitoring program, here’s the range map from the Cornell Lab or Ornithology’s All About Birds: