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adult Thayer's Gull
November
Nov 7, 2013. Davis, California. Photos by Steve Hampton.

This compares an apparent male Thayer's Gull (in the back) with an apparent female Herring (foreground). With regard to structure and bill size, they are very similar. Note the Herring shows a slight brow.

This compares two Thayer's Gulls with a large male first cycle Herring Gull.

December
Dec 2, 2013. Davis, California. Photo by Steve Hampton.

A petite female Thayer's surrounded by Herrings has a nearly pigeon-like structure.

Dec 17, 2011. Davis, California. Photo by Steve Hampton.
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 left wing).
January
Jan 4, 2015. Davis, California. Photos by Steve Hampton.

With California Gulls in front and probably Herring behind.


Herring (left); Thayer's (right)

Thayer's (right) with a probable female Herring on the left. Thayer's is ruled out by the black underside of the far primaries.


With California Gulls (left) and likely Gl-W x Herring (right).

Jan 9, 2016. Davis, California. Photo by Steve Hampton.
Thayer's (bottom) compared to California Gulls.


Jan 26, 2016. Davis, California. Photos by Steve Hampton.
Various birds in flight from below. Comparison with California Gull on far left.
February
Feb 6, 2014. Tiburon, California. Photo by Steve Hampton.
The bill, without a comparison to another gull, appears exceptionally strong for Thayer's.


Feb 6, 2016. Richmond, California. Photo by Steve Hampton.


Feb 6, 2016. Richmond, California. Photo by Steve Hampton.
With adult California Gull (left), adult Glaucous-winged or Gl-W x Herring, and first cycle Glaucous-winged (in back).
Feb 7, 2015. Davis, California. Photos by Steve Hampton.


These are two different birds, as evidenced by the slight differences in the white mirror on P9.

Feb 12, 2012. Sausalito, California. Photo by Steve Hampton.
This bird has a honey-colored eye, which is fairly common, and a rather long bill. Glaucous-winged Gull at left for comparison.

Feb 13, 2004. Chicago, Illinois. Photos by Kanae Hirabayashi.
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 14, 2014. Davis, California. Photo by Steve Hampton.
Probably a male Thayer's and a female Herring. The bill length is similar, but the Thayer's is thinner.

Feb 17, 2014. Davis, California. Photo by Steve Hampton.
Comparison with Herring Gulls.

Feb 18, 2012. Davis, California. Photo by Steve Hampton.
This is the pale extreme for eye color. 2nd cycle Glaucous-winged Gull provides a size comparison.

Feb 27, 2011. Davis, California. Photo by Steve Hampton.
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.

March

Mar 1, 2012. Davis, California. Photo by Steve Hampton.
Another comparison with Herring Gull. Note the large apical spots at the primary tips. This can be a good way to pick out Thayer's from a crowd.
Mar 16, 2001. Milwaukee, Wisconsin. Photo by John Idzikowski.
Another photo showing both upper and underwing patterns.