Mongolian Gull L. c? mongolicus

April 13th 2002 Sakawagawa-river Odawara Kanagawa Japan
Most large gulls were still identified as Vega Gull by their winter streakings. However, since the remainder showed white/whitish head and various features, they often confused me as usual. But this individual looked most suitable for mongolicus, among them. But unfortunately, I have no choice but to say, strictly speaking, identifications for adult mongolicus are usually pretty tentative, especially in spring.

mongolicus, and taimyrensis (left)

This individual has black markings on P10 to P4. This pattern can be seen oftener in mongolicus, though it is not unusual in vegae as well.

Vega Gulls L.vegae  on the same date.
Sakawagawa-river Odawara Kanagawa Japan
April 13th 2002 Sakawagawa-river Odawara Kanagawa Japan

Vega gulls tend to remain winter plumage until mid April.

Breeding plumage Vega Gull (?)

Somehow I felt this individual might be suitable to be Vega Gull rather than Mongolian Gull. But it is very difficult to identify them in breeding plumage.