An unusual Blackpoll Warbler

 

Yesterday morning I photographed this unusual adult male Blackpoll Warbler in the beach plum behind the north observation deck on Sandy Hook.

It was unusually early, for Blackpolls are normally among the last of the warblers to come through, although not unheard of early.

Assuming this is an adult male (based on its overall color, the strong malar stripe and the unstreaked black cap), it is unusual to show a white eye arc and a white supraloral. None of the guides I consulted mention the possibility of males showing these characters, and I had certainly never seen it before. These are characters more often associated with females of the species.

The throat and malar area look normal for the species. Male Blackpolls often have a few black feathers on the chin, as does this bird.

Here is the bird from another angle. I don't see anything unusual here either.

The bird was by itself and did not vocalize. It foraged quietly for insects in the beach plum.

Does this bird show a mix of mostly male and some female characters? Or is it a hybrid with another species? Or do male Blackpolls sometimes show eye arcs and a white supraloral?

Postscript:
Having thought about this a little more, it seems likely that this bird was not quite finished with its prealternate molt. In basic plumage it has that eye arc and the supraloral. Most wood-warblers have a prealternate molt early spring, as I'm sure does the Blackpoll.