Vega Gulls Larus vegae
March 26th 2004 Choshi Chiba Japan

 Vega Gulls seems to have a tendency to show more extensive grey area on their dangled primaries below the tertial crescent compared to Mongolian Gulls, though it is variable.

A relatively dark individual.

Same as above. Primary markings: P10-P4, like the majority of Mongolian Gulls.

The head streaking is fairly sparse in this individual. But it was not so really 'white-headed' in the field. And note that the individual on the left has very heavy streaking.

Same individual as above. Primary markings: P10-P5. The P5 marking is very small.

Primary markings: P10-P5.

Presumed breeding plumaged Vega Gull?
But I think some Mongolian Gulls can look identical to this individual. Identifications between the 2 forms are often very hard especially in breeding plumage.

Same individual as above. Primary markings:P10-P5, typical for Vega Gull, minority in Mongolian Gull.