Monday, November 16, 2009
Click the picture for a larger view.
Answer by Kevin Kerr and Tony Leukering
This week's two-bird quiz did not cause may problems for the regulars, nor for the few newer Mr. Bill Mystery Quiz afficionados. As Kevin Kerr provided a reasonable synopsis of the ID of the two not-so-wee beasties, I'll have him start us off.
"Assuming that I haven't missed something, I think that the identifications are actually fairly straightforward this week, despite the unusual appearance of two overlapping birds. The lower bird is a typical Black Vulture, thus the challenge is to identify the upper bird, whose body is mostly hidden. Luckily, there are lots of clues. The bird clearly associates with Black Vulture, is comparable in size to a Black Vulture, but has relatively pale wing and tail feathers, and with a longer, rounded tail. These features point pretty clearly to Turkey Vulture. Most other dark raptors would feature a banding pattern onthe tail and would be of noticeably difference in size."
At this point, I wish to do two things: 1) emphasize Kevin's point about the differing tail shapes and colors (long, rounded, and paler -- with the tail contrasting fairly strongly with the blacker undertail coverts -- in TV, short, square, and blacker -- no contrast to undertail coverts -- in BV) and 2) to elucidate the ID a bit further. While given good views of either species, the identification of these two vulture species is easy, odd lighting, distant views, and other negative impacts on views can lead the unwary down the wrong path. Except under the most backlit of conditions, the pattern of black and pale on the underside of the two is diagnostic, with the black/pale contrast being in the hand (the outer wing) and perpendicular to the wing in BV and the contrast in TV being parallel to the wing. Additionally, though a few respondents noted otherwise, the wing shape of the two species is fairly different, with BV having wider and shorter wings to TV's longer and narrower wings. Finally, the flap style of the two species is radically different, with TV exhibiting a long and somewhat ponderous wing flap and BV an almost comical quick, snappy, almost scared-to-fall-out-of-the-sky wing flap reminiscent of smaller accipiters. The relative wing lengths of the two species are the primary movers and shakers in the causes of these two very different wing flaps.
I photographed these two birds in West Cape May, Cape May Co., NJ, on 19 October 2009 gliding off a thermal. I provide the next picture in sequence, below, as proof positive of the two IDs. of course, if Lesser Yellow-headed Vulture had been on the ABA-area list, the ID of the top bird would have been just a wee bit more difficult!
Incorrect species provided as answers:
Chihuahuan Raven - 1
Ferruginous Hawk - 1
Zone-tailed Hawk - 1
The 18 of 21 providing the correct answer:
Answer: Black Vulture, Turkey Vulture