Monday, December 7, 2009

Quiz #327 (2009-4-09) Answer

Click the picture for a larger view.

Answer by Margie Joy and Tony Leukering

Most repondents spotted that this week's quiz birds were grackles and that the task was to pick the right species, with the vast majority going with one of the two of what I call "big-boy grackles." Margie Joy will start off the solution.

"Even in the dim light of this photo, with birds mainly in silhouette, there are enough clues for ID. Several of the birds have the large, flared tails of male grackles, and there’'s just enough light to show that they are all consistently dark or even black with no obvious marks, and that the eyes are light.

"There are three grackle species in the ABA area: Common, Great-tailed, and Boat-tailed. Following the advice of one of my drawing teachers (play it like the SAT -- do the easiest part first), I looked at the most obvious individuals, the ones with large, flared tails that are at least the length of the body. I ruled out Common Grackle, with its proportionately smaller tail, for those birds. Flattish heads with heavy bills eliminate Boat-tailed Grackle (a species with some individuals, but not all, having dark eyes, so separation by eye color is not reliable as we were not given the location), leaving me with male Great-tailed.

"The smaller birds with not-so-large tails are a bit more difficult; I'm still not 100 percent convinced about all of them. In general, they are smaller than the males, with shorter and narrower tails, typical of female grackles. I think they're all still too big to be Common, so the trick is to decide if they are Great-tailed, like the males; or Boat-tailed; or a mix of both. I can't see the entire head on all of them, but the ones I do see share the flattish head and thick bill shape of the males. So, I am going with Great-tailed Grackle for all."

Good job, Margie! As Kevin Kerr noted, the female in the lower-left quadrant with something in her bill is the individual that we can see best. She sports a
superciliary that helps us to eliminate Common Grackle in her ID and she has the streamlined head shape so typical of Great-tailed and so at odds with the round-headed appearance of Boat-tailed Grackle. Though folks on the East Coast think that Boat-tailed is a big grackle, my recent experience of switching between Colorado and New Jersey gave me a much better feel for the differences between the two big-boy grackles, including the much larger size of Great-tailed. So, if there is a Boat-tailed Grackle in the picture, it should appear noticeably smaller and none of the birds looks smaller to my eye. Additionally, as I took the picture near Barr Lake, Adams Co., CO (in December 2006), any Boat-tailed would have provided a first state record!

With two quizzes to go in the quarterly competition, Kevin Kerr is tied with the
two Such brothers with perfect scores (9 of 9). Six others have 7 of 9 correct;
none have only 8 correct.

Incorrect species provided as answers:
Common Grackle - 3
Boat-tailed Grackle - 5
Black-billed Magpie - 1
Common Raven - 1

The 17 of 26 providing the correct answer:
Al Guarente
Kevin Kerr
Andy Dettling
Mark Dettling
George Cresswell
Lynnette Fuller
Ray Davis
Margie Joy
Robert McNab
Su Snyder
Barbara Deneen
Nick Komar
Joe Bens
Tucker Lutter
Aaron Brees
Marcel Such
Joel Such

Answer: Great-tailed Grackle