Ok, I will start by saying that I have a lot of experience with MacGillivray's Warbler from my years of birding out west. I think this is a very interesting bird, but based on the two photos that were posted, I am not convinced that it is a MacGillivray's. I am leaning toward ID-ing it as an immature Mourning Warbler. Here's why: (1) The tail projection beyond the undertail coverts is much too short. In the first photo the tail length appears consistent with Mourning and could even be consistent with Connecticut. I have never seen a short-tailed MacGillivray's in the field (when I could get a good look at the tail, that is!). (2) Bona fide MacGillivray's have two heavy white eye crescents, above and below the eye, that are very well defined. The pattern on this bird as seen in the two photos is different-- it looks more like an interrupted eye ring that converges in front and in back of the eye more than I have seen in MacGillivray's. Indeed it looks like the eye ring might continue very faintly around the eye. This is a relatively bold pattern for a Mourning Warbler, but not inconsistent with reports of some strongly marked immatures of this species. (3) The whitish throat and color separation on the breast can be marks for MacGillivray's, but cannot stand alone without other consistent field marks. Also it is possible that the photographs overestimate the whiteness of the throat depending on exposure and lighting.
Obviously I did not see this bird in the field and others did. I have only seen these two photos and so it is possible that I am missing important clues that would be more evident in the field. I am not absolutely ruling out MacGillivray's, but I think that immature Mourning Warbler is a better overall fit to the data that I have seen. But let the discussion continue; Others may have different impressions/insights!
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On Aug 20, 2012, at 3:19 PM, Bryan Pfeiffer <[log in to unmask]> wrote:
> Greetings, VTBIRDers:
> Sorry to be late to the party, but one other thing to consider on the Mourning/MacGillivray's challenge is call note. It's fairly distinctive in the two species. Mourning issues an odd, flat, almost scratchy "chit" or "chet" note; MacGillivray's offers a short, sharp "tik" note. Not as easy as it may seem in writing, but it's something to consider if the bird resurfaces. Also note that hatch-year Mourning Warblers and even some female after-hatch-year birds can show narrow eye-arcs. But this bird, with its whitish throat and thicker eye arcs, does look pretty good for MacGillivray's. I don't like the tail proportions at all for MacGillivray's, but I'm less familiar with that as a field mark.
> Bryan Pfeif
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