unidentified gull - adult, Barton Cove, Gill, MA. January 29th, 2012. A curious looking bird with upperparts color a tone or two darker than most of the surrounding American Herring Gulls, but certainly not dark enough for a typical Lesser Black-backed Gull (also present). Legs were rather fleshy-yellow or perhaps orange toned, more striking in the field than they appear in these images. The weak yellowish tones to the legs do not show up well in these particular images.
Found late in the afternoon after I'd spent most of my time on Kumlien's and Glaucous Gulls. I'm not sure what to make of it, so I'm just posting the images for the time being. The situation wasn't helped by the fact that the bird was roosting almost the whole observation. It lifted its head just once when a flock of Canada Geese departed from the cove.