They do appear however to be fairly regular winter visitors to the CT River area near Gill and Turner's Falls in MA. Following a recent report of a sighting I was happy to find the gull there in a mixed group roosting on the ice.
What distinguishes them from other gulls are gray upper parts, yellowish legs, head and neck streaking, and a medium size bill that is slender and often tapered. They are much smaller than the Great Black-backed Gull and also smaller than the Herring Gull, standing behind it in this photo. The two gulls in front are Ring-billed Gulls.
In this year's Kumlien Gull, shown here in front of a Herring Gull. note the fresh gray upperparts indicating a second cycle individual. The bicolored bill confims this. The first cycle gulls in the photos below have a uniformly dark bill.
Also on my recent visit there I was fortunate enough to I observe two Ring-billed Gulls practicing synchronized swimming.
And here's a Herring Gull admiring her mirror image. Oops --sorry, it's upside down! :-)
Cheers and Happy Birding!
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Information based on Howell's and Dunn's "Gulls of the Americas" and on articles in Wikipedia.org. Strangely Cornell's Birds of North America had no listing for the Lesser Black-backed Gull.