Friday, August 26, 2016

August Warblers

Fall Warblers are notoriously difficult, but not impossible, to identify. They are often referred to as CFW’s, Confusing Fall Warblers. Here I post six I banded in Northfield on 22-23 August 2016. I have linked each to previous blog posts showing spring birds and to some ecological notes. Here I discuss only their field marks. The first photo is of a Golden-winged Warbler. Because in the fall this species looks similar to spring birds, this CFW is one of the easier ones to identify. This warbler is a female, and is easily recognized by its dark cheeks, yellow crown, and golden wing bars.

This second warbler is also not difficult. Canada Warblers are proclaimed by their golden lores, white eye rings, and black necklaces. Males have darker necklaces than females, but many fall birds are intermediate, making sexual identification difficult.
This third bird is a hard one. The gray head, white eye ring, and pale throat proclaim it to be a Nashville Warbler. Even in the fall, many Nashville Warblers have much brighter yellow throats than this drab-plumaged immature. In the two days that I took these photos, I banded 32 birds—20 were Tennessee Warblers.
Chestnut-sided Warblers are a bit easier. Their gray underparts contrast with their white eye-rings. Their crowns are bright yellow, such as occasionally found in tropical tanagers.

Tennessee Warblers show considerable variation.  Often they are muted shades of yellow. This gray-headed individual is one of the few adult warblers I banded this August. In any plumage, a good key to identification is the black line through the eye. The predominance of young birds has me a bit puzzled.

This final bird is the toughest of the lot to identify. Note the bright yellow underparts and weak white line surrounding the eye. The bill is relatively robust, at least compared to the other warblers on this page. One key to the identity of this Mourning Warbler is the dark line below the throat. 

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