Slaty-backed Gull Larus schistisagus
16th October 2002 Sakawagawa-river Odawara Kanagawa Japan
Juv/1stwinter. Primaries are brownish, not black.
Same bird as above. But in this situation, it looks blackish like Vega Gulls because of the light condition.
A diffrent individual.
Vega Gull (left), Slaty-backed Gull (right)
A dark individual resembling simithsonianus. But the primaries are not really blackish in better light.