adult Thayer's Gull

adult
Thayer's Gull

Fig 1) This remarkable photo shows the unique primary pattern of this species. On the upper wing, note that the black is largely confined to the outer webs, except for the subterminal bands. On the under wing, the wing appears fairly white except for the dark subterminal band on the outer primaries. Note also the dark eye and dark pink legs. Feb 13, 2004, Chicago, Illinois. Photo courtesy of Kanae Hirabayashi.

Fig 2) The same bird as above. The dark subterminal band on the outer primaries is easy to see on soaring birds.

Fig 3) Again, the same bird as Figures 1 and 2. By this time in winter, the extensively smudged hood is turning rather white.

Fig 4) Another photo showing both upper and underwing patterns. This is a different bird from above; note the slight differences in the primary pattern. March 16, 2001. Milwaukee, Wisconsin. Photo courtesy of John Idzikowski.

Fig 5) Comparison with Herring Gull. Based on head shape, both of these birds are probably females; the mostly-obscured bird directly behind the Thayer's may be a male Herring. On the Thayer's, note the more dove-like head shape, shorter bill (appearing paler only because the Herring in comparison is already turning brighter yellow), dark eye, and pale underside to P10, visible on the underside of the folded wingtip. February 27, 2011. Davis, California. Photo courtesy of Steve Hampton.

Fig 6) Note the smudgy head and neck markings, the darkish eye, the greenish tinge to the yellow on the bill, the mantle shade of gray (slightly darker than smithsonianus Herring) and the pale underside of P10 (on the right wing). December 17, 2011. Davis, California. Photo courtesy of Steve Hampton.

Fig 7) This bird was photographed in February in Japan, where Thayer's Gulls are rare but regular. Note the nice hooded look (though it's beginning to fade), the pale underside of P10 (on the far wing), the dark pink legs, and the rather small bill. Photo courtesy of Nobuo Matumura.

Fig 8) The size difference between this apparent female Thayer's and the apparent male Glaucous Gull behind it is astounding. On the other hand, male Thayer's Gulls are very similar in size and structure to a female Herring Gull. March 16, 2011. Davis, California. Photo courtesy of Steve Hampton.