Friday, September 28, 2012

"Fri-D" - Bay-breasted V. Blackpoll Warblers

 [Above, first fall Bay-breasted Warbler, Cape May Point State Park, NJ, Monday, September 24, 2012. Below, first fall Blackpoll Warbler, Cape May Point, October 2011. Click to enlarge, and compare underparts color, upperparts color, wingbars, face.]

When you bump into one of these drab, wing-barred fall warblers, how (after making sure it's not a Pine Warbler) do you tell which of this famously challenging pair you have?

Leg color works when you can see it, which you can't well enough on the upper bird. By well enough we mean seeing the feet, and specifically the soles of the feet. Blackpoll often has yellow legs, almost always has yellow feet, and always has at least yellow soles of the feet, while Bay-breasted has dark legs and feet.

Underpart color is very usueful, with Blackpoll less richly colored and with clean white undertail coverts. This Bay-breasted, probably a female, isn't showing much of anything in the way of bay on the flanks, maybe just a tinge of pinkish, but has more extensive yellowish buff below. And above, too - upperpart color on Blackpoll is grayer, and they have a grayish neck compared to Bay-breasted's yellowish buff.

Compare the wingbars - Bay-breasted's are wider, a very good clue. Compare the face pattern - subtly different, with Blackpoll having a more defined eyeline and Bay-breasted a more obvious yellowish eyebrow.

You'll read how Bay-breasted either has no streaking above, or has fainter streaking, but clearly that isn't working here. Ditto streaking below, with both birds showing muted streaks. This is a mark I've cooled on over the years.

As with anything else, collect multiple field marks before making your call.

[Below is an easier fall Bay-breasted, a male, probably first year, photographed the same day and place as the Bay-breasted above.]

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