Monday, June 21, 2010
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Answer by Tony Leukering
Michael O'Brien provided this week's quiz picture from his VENT chicken tour this April; he thought that it might cause some problems. He took the picture near Campo, Baca Co., CO.
Most respondents went with the sparrows, with one waiting and waiting for the bird to turn around, to no avail. The Carpodacus finches can be quickly ruled out by our bird's short primary projection; the finches all have long primary projection with numerous primaries extending beyond the tertials (what primary projection there is is enough to rule out Lark Bunting). Also, as Chuck Carlson noted, the lack of any white in the center of the crown should do the job of eliminating the "grassland" sparrows that might have caused confusion (Savannah, Grasshopper, Baird's). The tail length and individual rectrix shapes also do that job for all and the primary projection rules out Savannah. After all the above, the heavy flank streaking extending onto the lateral undertail coverts leaves us with just three options: Vesper, Song, and Lincoln's sparrows. The last of these is eliminated by that species having blackish flank streaking overlaid on buffy feathers. Since the bird seems to entirely lack white in the tail, the answer should be Song Sparrow.
As I am not a particular fan of ID by elimination, let's check other features. The most noticeable on a bird that is nearly entirely of the same color tone, is that block of dark median coverts with strong white tips. This is not a feature of Song Sparrow, which has strong rufous or warm brown fringes such that the median coverts are of the same color tone as the rest of the wing, with thin whitish tips. Vesper Sparrow, however, matches that characteristic precisely and while our eyes are captivated by that distinct dark panel, we might notice the suggestion of rufous lesser coverts. Though Vesper Sparrow sports such, that feature is not necessary in our ID process, as the median coverts are so distinctive for the species. But, what about the white outer rectrices that are also typical of Vesper Sparrow? Well, as noted by Margie Joy, when the rectrices are stacked like this and as our view is from above, the white outers are hidden by dark inners, though we can see just the very edge of the white on the outermost rectrix on the bird's left side.
Incorrect species provided as answers:
Purple Finch - 1
Song Sparrow - 2
Savannah Sparrow - 3
Cassin's Finch - 1
Lincoln's Sparrow - 1
Congratulations to the 8 of 16 getting the quiz correct:
Answer: Vesper Sparrow