“Brewster’s” Warblers are hybrids between Golden-winged and Blue-winged Warblers. You can read an article about these hybrids from the American Birding Association’s magazine Birding here.
Here are a couple of the “Brewster’s” Warblers banded at RRBO.
This bird was banded on 6 May 2004. This bird has a yellowish throat, white rather than yellow wing bars, a whitish rather than yellow throat, and a white rather than yellow underbelly. The back had only a tinge of green.
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This male was banded on 5 May 2002 at RRBO. It had yellowish wing bars and a fully yellow throat throat.