Sunday, September 5, 2010

Bay-breasted Warbler

Saturday noon my bird nets finally intersected with a mixed species flock of warblers.  The most interesting of these were two Bay-breasted Warblers, one of the most difficult to identify Confusing Fall Warblers.  Even experienced birders can have trouble telling apart Bay-breasted, Blackpoll, and Pine warblers.  Blackpoll warblers will almost always show at least some yellowish on their legs, even if restricted to the underside of their soles.  The other two birds have gray feet.  This warbler definitely sported gray feet and toes.
Pine Warblers, unlike Bay-breasted, usually show brighter "spectacles"--eye rings with a line attched to the bill area.  Pine Warblers also usually show at least faint streaking on their flanks.  Finally, Pine Warblers in comparable plumage are usually not as bright as Bay-breasted Warblers. My photo shows none of these field marks.  Finally, Bay-breasted Warblers often show a hint of chestnut on their flanks, which can almost be seen on my bird.

Bay-breasted Warbler numbers fluctuate with outbreaks of spruce budworms in the north woods.  The spraying of Canadian forests for budworms have hurt Bay-breasted Warbler populations.  Bay-breasted Warbler migrate across eastern North America. They continue to northern South America across the Gulf of Mexico.  Blackpoll Warblers, on the other hand, migrate across the western Atlantic Ocean.  Consequently, Bay-breasted Warblers are less often observed in the southeast United States (Williams 1996).

2 comments:

  1. I wonder if you could comment on the amazingly complex looking feet of the Warbler. Why does that rear claw curve forward so much? The feet above look like they are lightweight for flight, but highly evolved. These feet look different from other bird feet I have seen. How are they used by the Warbler other than to grasp a branch?

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    1. The photo is an extreme close-up, so its bigness may be somewhat of an optical illusion. I think it is not functionally different from other bird feet. The point of the photo is that this foot lacks the yellow usually seen on Blackpoll toes.

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