Monday, March 7, 2011

Quiz #389 (2011-1-10) Solution

Click on picture(s) for a larger view.

Answer by Tony Leukering

Like last week's quiz, our choices quickly devolve to two options. This week, it's the black head and wings, rufous sides, and buffy undertail coverts that do that trick. Now, which is it, Spotted Towhee or Eastern Towhee? I've played with this duo a few times on the Mr. Bill Mystery Quiz, because they can be genuinely difficult and many birders do not fully understand all of the relevant field characters. And, of course, they hybridize in the central Great Plains.

What we can see of the wing coverts -- granted, not much -- reveals no spotting that would be typical of Spotted Towhee. However, recall that there is an unspotted (or mostly so) form of Spotted Towhee. But, I used that form fairly recently; would I do so again so soon? Hmm. Well, we can quickly rule out that little-spotted form of Spotted Towhee, as our quiz bird sports gigantic white tail spots taking up 3/4 of the length of the tail; that northwestern form of Spotted has considerably smaller tail spots. In fact, those extensive tail spots should rule out all Spotted Towhees except for the plains-breeding race, arcticus.

The important aspect of the view we get of this week's quiz bird is the primaries, and I provide an enlarged version of that part of the bird, below. Spotted Towhee has relatively little white in the primaries, with that color being restricted there to the leading edge of the outer primaries, but only the distal 1/5 to 3/4 of the length of individual primaries; that white does not extend to the primary coverts. Eastern Towhee shows at least one primary -- often, a few primaries -- on which the white leading edge extends the visible length of the primary and meeting the large patch of white at the base of the outer primaries adjacent to the primary coverts.

As can be seen on the enlarged inset, above, the white edges of many of the outer primaries extend to the white patch at the base of the primaries, which is indicated by the arrow. The important aspects of "Rufous-sided Towhee" ID is not presence vs. absence of white, they are the extent of white and where, precisely, the white is.

I took this picture of an immature male Eastern Towhee at Chico Basin Ranch, El Paso Co., CO, on 8 April 2006. Mark Peterson and I found this bird on 6 January 2006 while conducting the local Christmas Bird Count. This individual was the cause of the Long-billed Thrasher that wintered at this site being found, as Brandon Percival went there to check out our rare Eastern Towhee and found the thrasher! Below is a picture I took of the same individual on the day that Mark and I found it. In it, one can see that the primaries are noticeably browner than are the wing coverts, indicating its immaturity.

Incorrect species provided as answers:
Spotted Towhee - 7

Congratulations to the 18 of 25 getting the quiz correct:
Tyler Bell
Chuck Carlson
Ben Coulter
Nick Komar
Pam Myers
Christian Nunes
Ali Iyoob
Su Snyder
Gary Koehn
Robert McNab
Peter Wilkinson
Matt Bristol
Joe Bens
Joel Such
Marcel Such
Bryan Guarente
Devich Farbotnik
Thomas Hall

Answer: Eastern Towhee