[Maine-birds] possible Thayer's Gull, Fairfield 20 Jan

This afternoon I found an immature gull that shows characters of a Thayer's Gull. It was part of the collection of gulls resting above Shawmut Dam. (This is north of I-95 on Rt 201; access by going to the east end of Kennebec St. and turning left, then walking up to look over the area above the dam.)

The key characters are the wings, which show dark brown primaries with whitish fringing at the tip and pale inner webs. The underside of the primaries is silvery-gray, and when the bird raised its wings showed as mostly translucent with prominent dark trailing edge formed by dark tips. The bird looks like a dark version of an Iceland Gull in size and shape and underwing pattern, but at rest, the wingtips are quite dark, almost as dark as an immature Herring Gull. A number of other characters seem right for Thayer's, but I hesitate because the bird looks short-legged for the species, among other minor things. (Iceland is the shorter-legged of the Thayer's/Iceland pair.) The small size is a function of sex, and the petite, rounded head suggests the bird is a female. There are plenty of Iceland Gulls to compare, 24 similarly aged birds were there today, and I had 38 Iceland Gulls a couple of days ago. Also present today was a single Glaucous Gull. I did not see the adult Lesser Black-backed or hybrid Herring x Lesser Black-backed that have been here.

I think this bird deserves further study and may prove to be a Thayer's Gull, which has only been recorded twice before in Maine:
https://sites.google.com/site/mainebirdrecordscommittee/official-list-of-maine-birds/thgu

Here are some highly cropped images (4 total, click newer to see the others or pick from gallery in photostream):
https://sites.google.com/site/mainebirdrecordscommittee/official-list-of-maine-birds/thgu

Louis Bevier
Fairfield

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