Black-throated Blue Warbler forms at Cape May

Good numbers of Black-throated Blue Warbler passed through Cape May and Higbee Fields during the last couple weeks (eg 66 counted at Higbee Dike on Fri 5th October alone).  An experienced birder mentioned to me that the local male population has a plain mantle compared to the Appalachian form which has some faint streaking on the mantle.  I checked through some images and sure enough, there are variants.  Apart from this interesting factoid, the species is indeed stunningly photographic, even in the Autumn.  I've included a couple images of a first year female which shows just how sexually dimorphic this species is.