Slaty-backed Gulls Larus schistisagus
March 15th 2005 Choshi Chiba Japn
Same individual as the left bird in the above 2 photos
In the individual in front, replaced feathers seem to be restricted to the upper scapulars/mantle.
Same individual as the front bird in the above photo.
Note the typical brownish primaries.
Same individual as above
3 Slaty-backed Gulls
4 Slaty-backed Gulls
Note their variable brownish (not blackish) primaries .
One Glaucous-winged Gull among Slaty-backed Gulls.
Glaucous-winged Gulls tend to look obviously grayish and uniform than Slaty-backed Gulls
2 Slaty-backed Gulls, and 1 Glaucous-winged Gull (right).