Black-throated Green Warbler (Dendroica virens), GIlbert Water Ranch, Maricopa County

This Black-throated Green Warbler was discovered and photographed by Brendon Grice on 11 November 2009 at the Gilbert Water Ranch.

Prior to 1990 there were about 30 records for Arizona, but it has been much scarcer since with only about eight records. This pattern of decreased occurrence since 1990 seems to fit several other northerly breeding eastern warblers that are much less common as vagrants to the state than previously.  However, in the past couple of years it seems that the number of records of this species may be increasing. 

Identification of Black-throated Green warbler in this plumage is fairly straightforward. It is a bird with a bright yellow green face, darker ear patch, bright green unstreaked back, prominent white wingbars and mostly grayish white underparts with blackish streaks down the side and with at most only a faint yellow wash below. The two most likely confusing species are Townsend’s and Hermit Warbler. Hermit usually has plainer face, grayer back and lacks streaking on the sides. Towsend’s has a more contrasting face, often streaking on the back and usually a much more yellow upper breast. Either a very dull immature Townsend’s or a Hermit X Townsend’s Hybrid are likely to cause the most confusion. In these and all cases the wash of yellow across the vent just behind the legs is diagnostic for Black-throated Green.

11 November 2009, photos by Brendon Grice