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:
Answer: Brown-headed Cowbird