Monday, September 12, 2011
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Solution by Tony Leukering
Respondents were split with this week's quiz bird between Empidonax flycatchers and vireos, with most opting for the latter, though with four species of vireo submitted as answers. Presumably, the thicker bill with a strong point and no yellow on the mandible and the bluish legs were features that those in the vireo camp used to arrive at that destination. Empidonax tends to black legs, with Least and Gray having decidedly black legs. The strong gray and white tones to the bird encouraged most respondents into the Plumbeous/Gray/Bell's trichotomy (Cassin's always shows yellowy-green flanks, at least), with the majority selecting the correct option. As Thomas Hall noted, "The double broken eye-ring leaves only one choice."
Yes, focusing on the face, we can see that the bird has a white supraloral area -- which all three sport to some extent -- and a very thin dark eyeline splitting the eye ring both in front and behind and creating eye arcs. Plumbeous' eye ring is split only in front and Gray's eye ring is complete. So, two breaks = Bell's; one break = Plumbeous; and zero breaks = Gray.
Steve Mlodinow took this picture of a Least Bell's Vireo near the tip of Baja California, Baja California Sur, Mexico, in March 2011.
Incorrect species provided as answers:
Least Flycatcher - 1
Gray Vireo - 5
Plumbeous Vireo - 2
Gray Flycatcher - 1
Cassin's Vireo - 1
Congratulations to the 15 of 25 getting the quiz correct:
Answer: Bell's Vireo