Monday, June 29, 2009
Click the picture for a larger view.
Answer by Tony Leukering
The apparent smallness and yellowness of this week's quiz bird suggests that it just might be a warbler and the pink legs probably makes that a certainty. Despite that many think of warblers, in general, as yellow, there are very few with this much yellow, given the view we've got, and that lack obvious field marks below. The solution set of such includes Blue-winged, Yellow, Prothonotary, Kentucky, Hooded, and Wilson's warblers.
The apparent yellow primary fringing and outer webs to the greater coverts certainly suggest a Yellow Warbler and, with that species being such a common and widespread species, just on chance alone. Throw in the obvious green head and back, and it would be a good match for a adult female (it's too bright for an immature female) or immature male (it lacks the rufous streaking of an adult male) Yellow Warbler. However, I'm going to cut to the chase here and point out the tail. It only occupies a small percentage of the frame, but it is incredibly important at cutting down the options. What we can see of the tail looks solid green and, because we're looking at the underside, we can see that the bird lacks tail spots (paler areas on the inner webs of the rectrices of many warbler species). This, alone, rules out Blue-winged, Yellow, Prothonotray, and Hooded warblers.
Because of the position of the head, we cannot discern the facial pattern in order to get to the ID among our last two candidate species. So, we'll have to look elsewhere, but where would that be? These two species are amazingly similar, given this view. If we could discern tail length, we would find it most helpful, as Kentucky is short-tailed and Wilson's is long-tailed. But, that datum is not available to us because of the photo's angle. I had to study field guides to find the certain key to the bird's ID: flank and side coloration. Kentucky Warbler has olive sides and flanks, while Wilson's has a brighter yellow patch near the bend of the folded wing. Brandon Percival took this picture -- and the one below -- of a male Wilson's Warbler 9 September 2007 at Pueblo Reservoir S.P., Pueblo Co., CO.
Because we can see the crown patch fairly well on the bird, we can be certain that it is not a female. Eastern females completely lack crown patches, while western ones can have small to quite-large patches. However, even females with the largest black crown patches don't sport such smooth, evenly-bordered patches; their patches have very ragged rear edges. This bird has a number of the feathers at the rear of the patch edged in yellow, suggesting that it is an immature male (hatched the previous summer) rather than an adult male, which tend ot have no yellow edgings or just a few of them.
Incorrect species provided as answers:
Hooded Warbler - 4
Kentucky Warbler - 8
Painted Bunting - 1
Mourning Warbler - 1
The 9 of 23 providing the correct answer:
Answer: Wilson's Warbler