Photo taken in northwestern Arizona at the end of April.
Answer will be displayed on July 1.
Answer:
The white eye ring and wingbar patterns, plus shape tell us that it is
some kind of vireo. The possible vireos in this area are Bell’s, Gray,
Cassin’s, and Warbling.
The dark gray color eliminates Warbling and Bell’s. That leaves Gray,
Cassin’s, and Plumbeous. On Gray Vireos, the dark area of the head
doesn’t get close to the throat, but becomes lighter. However, we can
see that the dark extends much farther down, and continues until just
before the bill. So it is either Plumbeous or Cassin’s. Note that
Plumbeous’s belly is light gray, whereas this bird’s belly is
white. Cassin’s Vireos have a yellow wash on the undertail
coverts, which is present. This plumage variance is only found in
Cassin’s Vireos. (Also, Cassin’s’ wings are partially green, and
Plumbeous’s are grey, but they are blocked by a stick in this photo).
This one is tricky. Congratulations to Riley and Ben for figuring out
Cassin’s Vireo!