Monday, November 23, 2009

Quiz #325 (2009-4-07) Answer


Click the picture for a larger view.

Answer by Kevin Kerr and Tony Leukering

Wow, lots of birds in this quiz picture! And, with my rep, folks probably spent a lot of time sorting through the birds looking for something hidden amongst all of the Brown-headed Cowbirds. Kevin Kerr sent in another thorough answer, so he will do most of the job of answering this week's quiz.

"Uh oh! It's another one of those pictures. Where's Waldo? The flock is quite sizable this time and more intimidating than say, terns on a dock, or snakes on a plane. I decided that it's time to model a new approach to these pictures, though I suppose this is just a classic approach to identifying large flocks. First, identify an obvious bird, one displaying a good diagnostic profile. Two birds in flight do this nicely: clearly male Brown-headed Cowbirds. A few of their drabber female companions are also in clear view. In fact, at quick glance it appears that most if not all of these birds are Brown-headed Cowbirds. So, now we have a null hypothesis for each individual: it's a Brown-headed Cowbird until proven otherwise.

"But there's got to be more than that, right? Judging by the yellowing plants in the background and fallen leaves, I'm assuming this picture was taken in autumn. Naturally, cowbird flocks are likely to contain other Icterids, so it would be wise to look for such. Any tiger-barred bodies out there? Any bronzed feathers or keel-shaped tails? To the far left, it looks as though a yellow-bordered epaulet is peeking out of the crowd, but alas I think it is just an illusion caused by a blade of grass and not a Red-winged Blackbird. A small brown job facing us in the centre of the photo could be mistaken for a female House Sparrow, but most of the colours aren't right and again, it appears to just be my imagination. Now I'm trying too hard to see species that probably are not there.

"Negative results are inherently difficult to prove, but I cannot find a bird in this photo that displays enough cues to suggest that it is not a Brown-headed Cowbird. So I'll have to conclude that there are no other species present."

Thanks, Kevin. Both of the birds that Kevin mentioned that might be something else (and I thought that if they were something else, they would both be Red-winged Blackbirds), are birds that I noted when looking at the original picture considering whether to use it as a quiz picture as I had intended when I took the picture. In the field, the flock was about 1100 birds strong (this picture depicts only a small percentage of the total flock). There were six Red-winged Blackbirds in the flock, along with a very small smattering of European Starlings and a few Common Grackles. When taking the picture, I purposefully avoided all parts of the flock that sported other species -- I wanted a single-species flock for the picture, which I took in Cape May Point, Cape May Co., NJ, on 15 November 2009. Despite the chance that the two birds are not cowbirds, I believe that I managed to not include anything but Brown-headed Cowbirds in the picture -- what we can see of these two birds is just not enough, in my opinion, to justify identifying a second species.

One respondent's answer was precluded from being correct for the competition, as it included none of the requisite two capital letters.

Incorrect species provided as answers:
Shiny Cowbird - 2
Red-winged Blackbird - 2
Brewer's Blackbird - 1
Rusty Blackbird - 2
Rusty/Brewer's Blackbird - 1
Bronzed Cowbird - 1

The 13 of 21 providing the correct answer:
John Bissell
Kevin Kerr
Nick Komar
Ira Sanders
Tammy Sanders
Al Guarente
Mary France
Margie Joy
Barbara Deneen
Marcel Such
JOel Such
Aaron Brees
Chishun Kwong

Answer: Brown-headed Cowbird

Monday, November 16, 2009

Quiz #324 (2009-4-06) Answer


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."

Thanks, Kevin.

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:
Aaron Brees
Kevin Kerr
Al Guarente
Nick Komar
Bryan Guarente
Louie Toth
Marcel Such
Peter Burke
George Cresswell
Margie Joy
Joel Such
Mark Dettling
Peter Wilkinson
Su Snyder
Bob Archer
Jennifer Vieth
Joe Bens
Chishun Kwong

Answer: Black Vulture, Turkey Vulture