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first winter/ summer Thayer's Gull

Fig 1) That's a smithsonianus Herring Gull on the left, and a rather petite pale Thayer's on the right. One is tempted to say it's a Kumlien's Iceland Gull or at least an intergrade, especially noting the patterning in the tertials. However, by late winter these birds fade quite a bit, making it tough to decipher how dark they once were. Also, I say "first winter/summer" because it now seems that Thayer's retain juvenile plumage through winter and then do just one post-juvenile moult (into "first winter/summer") prior to the complete moult into second winter. See the letter posted on this page for details on moult timing. March 8, Bay Area, CA. Photo by Mike Rogers, copyright 2000.

Fig 2) This is the same bird as above. In flight, it looks like a typical Thayer's Gull, with a dark tail band, outer primaries, and secondaries. The pale inner webs of the outer primaries (illustrated on the webpage background) are largely hidded by the angle of our view. Photo by Mike Rogers, copyright 2000.