Monday, July 12, 2010
Click on picture(s) for a larger view.
Answer by Tony Leukering
Almost all respondents got our quiz bird to the genus Icterus, the orioles. The strongly bicolored (black maxilla, blue mandible) bill is the single best clue to get there, once one rules out the Passerina buntings (including Blue Grosbeak). That bill color also helps us eliminate one oriole option, Altamira, but that species doesn't have a yellowish or greenish plumage at all, so it's out the door, anyway.
The overall impression of the bird's bright coloration is that of a yellow/green/orange, but with a distinctly dark back and two whitish wing bars. These features rule out four of the ten ABA-area orioles, leaving Orchard, Hooded, Streak-backed, Bullock's, Audubon's, Baltimore, and Scott's.
At this point, ageing the wee beastie might assist with identification, so let's tackle that. One of the more notable aspects of the quiz bird's plumage is the wear that is so evident on the head (the crown is mostly gray!) and in the wings: they're really brown and with the wingbars in fairly sad shape. Unless the picture was taken in late summer, this amount of wear would suggest an immature bird in its second calendar year. Looking closely at the greater coverts, we can see that at least some of the outer ones have centers noticeably darker than the paler and browner inner coverts, another good clue to immaturity. Finally, the bird's tail provides a similar clue, as the outermost rectrix on each side is more rounded, grayer, and sports an obvious and unworn white fringe to the tip than are the rest of the rectrices. Checking into Pyle (1997), we find that the pre-formative molt (called therein the first pre-basic; but terminology of these molts changed after the publication of the book, so...) in this species (I won't say, yet, what that species is) is eccentric, with an odd and variable variety of flight feathers replaced. That certainly matches our bird, so we can safely presume that this is a first-cycle female, as a similarly-aged male of the various orioles still in contention would have some male-like aspect (specifically, black on the throat) in late spring/early summer -- and the picture has to have been taken at this time from the plumage's appearance.
Our bird's back can help us to eliminate another few species, Streak-backed, Baltimore, and Scott's, as, if anything, it is barred, not streaked. Studying the face allows us to rule out Bullock's, as the brightest plumage there is behind the auriculars, not in the front of the face as it should be on Bullock's. Another character assists with that elimination: the pale edges of the secondaries. On Bullock's, these edges extend all the way to the greater coverts, whereas our bird's edges do not. There is a gap similar to that that allows quick separation of Ruby-crowned Kinglet and Hutton's Vireo, though not quite as obvious as on the kinglet. Quite fortuitously, this feature also eliminates Hooded Oriole, leaving us with the correct ID.
I took this picture of an immature female Orchard Oriole at Jumbo Res., Logan Co., CO, on 19 June 2010. Though virtually every respondent that got down to the Orchard:Hooded dichotomy got the correct species, few of those told me how they got there, so I don't know what features that most used to get the correct answer. I still think that most birders greatly underappreciate how difficult females of these two species can be to identify. Success in the endeavor requires careful scrutiny of a number of features, some of which can be difficult to assess correctly. Maybe I'll run a string of pictures of the two species for the next few quizzes, just to see how things go! Maybe not.
Incorrect species provided as answers:
"Yellow finch" - 1
Scott's Oriole - 1
Hooded Oriole - 1
Baltimore Oriole - 1
Bay-breasted Warbler - 1
Congratulations to the 18 of 23 getting the quiz correct:
Answer: Orchard Oriole