Monday, May 16, 2011
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Solution by Tony Leukering
This week's quiz bird was considered, without exception, to be a member of the small sparrow genus Melospiza by the week's respondents, who covered all the bases and provided all three species as answers. Of course, unless the bird is a hybrid, only one species can be correct, but the trick is how to tease that correct answer out of the fairly minimal -- though eminently typical -- view of a bird of a fairly retiring genus.
First off, even ignoring the apparently dense habitat in which our quiz bird is perched, we can quickly determine that the species is a denizen of thickly-vegetated habitats by looking at the wingtip visible. It is obviously quite rounded, with the four longest primaries being all nearly the same length. This is a typical feature of species that would prefer not to wear away their primary tips by beating them against the leaves and stems so prevalent in dense habitats. In case we were considering them, that fact can rule out longspurs for us.
If we can prove that the bird is not in juvenal (= first basic) plumage, then we can rule out Swamp Sparrow with its minimal streaking and strongly rufescent flanks. However, the softness of the focus on the quiz bird (the camera obviously considered the alder leaves to be the picture's subject) makes it difficult to discern the structure of the undertail coverts feathers, which would be soft and much more barbless than those of older birds, though I would still lean toward those feathers not being juvenal feathers. However, there is another way to determine the bird's age, even more generally than juvenal plumage vs. all other plumages. In Melospiza, individuals that are less than 14 months old and haven't completed their 2nd prebasic molt have a green cast to the gray on the head. It is weaker or stronger among individuals, but it is always present. Our bird lacks that green cast or tinge; its superciliary and cheek are smoothly gray. Another feature can confirm our decision to eliminate Swamp Sparrow from consideration, and that is the back. On Swamp Sparrow, the black streaking is so wide that it implies a dark back with paler streaking, unlike our bird's palish back with dark streaking.
Now things get really tricky, as much of the plumage often considered critical for separating Song and Lincoln's sparrows is behind those well-focused alder leaves: the malar region and the chest. But, as is often the case in the CFO Photo Quiz, I am very much interested in those features that are not used by most birders to ID birds, but which still provide perfectly useful ID information. And at this point, I want to point out that most of the benefit that I get out of conducting this quiz (I am a volunteer, just as all of CFO's principals are) is when it becomes obvious that I have had an impact on even one birder's understanding and knowledge. This week, Burke Angstman provided that hit of gratification to me with the following:
"Since I'm new to the CFO Photo Quiz I have been reviewing some of the previous quizzes and what I was able to find was an excellent photo of a Lincoln's Sparrow taken by Rachel Hopper and presented by you in Quiz #308. (This was really one of the best photos of a Lincoln 's Sparrow I was able to find.) Your description of the Lincoln's Sparrow included this statement:
'But, the color of the streaking on the undertail coverts (and on the flanks) is black, not the reddish color of morphna or most other races of Song Sparrow.'"
Indeed, Burke hit on the very feature that I planned on using to explain why this week's quiz bird was a Song Sparrow, rather than a Lincoln's Sparrow. The photographer, Terry Gray, reeled off four quick pictures of the subject in Latah Co., Idaho, on 9 October 2010, in the possibility that it was a late Lincoln's Sparrow. This photo, which was really the only useable one, came to me when Terry was searching for assistance in the bird's ID and I immediately recognized the photo-quiz potential of the picture. Because, as the long-time participants of this quiz know, I like to throw in difficult pictures of very common species. That is because, to really excel in identification, one really does need to know the common birds cold! Thanks, Burke!
With the devastation wreaked on the leader board by this quiz photo, Christopher Hinkle emerged as the sole respondent with a perfect score for the quarter.
Incorrect species provided as answers:
Lincoln's Sparrow - 13
Swamp Sparrow - 2
Congratulations to the 7 of 22 getting the quiz correct:
Answer: Song Sparrow