Monday, December 14, 2009
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Answer by Tony Leukering
This week's quiz bird is obviously a warbler; obvious, at least, to all of our respondents. The bird's coloration and small size makes that a good choice of starting point. Most quickly got to the genus Oporornis, as the fairly strong bill, olive upperparts, yellow underparts, and eye ring all point in that direction. Orange-crowned Warbler has a very fine and slightly decurved bill and neither it nor Wilson's Warbler show such an obvious chest band.
Once into Oporornis, we don't have an easy job of deciding the ID, though we can quickly rule out Kentucky Warbler. We have a huge advantage with this bird, relative to many Oporornis warblers, as the bird is in hand, not skulking about in the understory giving only brief and frustrating views. The bird's eye ring can actually allow us specific ID of the quiz bird, though we'll also tackle other field marks as confirmatory features.
The eye ring is obviously split, at least behind the eye and, probably, in front of the eye. This fact and that the eye ring is not bright white rules out the prince of the group, Connecticut Warbler. With the eye ring being split, we can state that the bird has eye arcs. The eye arcs are thin, very long (that is, each covers a significant chunk of the 180 degrees of its representative half of the potential eye ring), and have a yellowish cast. All of these features are bang-on for Mourning Warbler and quite wrong for MacGillivray's. The confirmatory features include the yellowish rather than grayish throat (ruling out both other options) and the short primary projection (length of the wingtip protruding beyond the tip of the longest tertial), which rules out the very long-winged Connecticut Warbler. I took this picture of an immature Mourning Warbler at Barr Lake S.P., Adams Co., CO, on 25 September 2001; the bird provided only the sixth fall Colorado record.
The leader board has not changed from last week, as all players in the hunt for the quarterly title got this week's quiz correct. Aaron Brees continues to lead all players for the annual competition. One quiz to go for both competitions -- good luck to all!
Incorrect species provided as answers:
MacGillivray's Warbler - 1
Wilson's Warbler - 1
Orange-crowned Warbler - 1
Connecticut Warbler - 2
The 20 of 25 providing the correct answer:
Answer: Mourning Warbler