Mongolian Gull, Choshi, Japan.

This bird, seen on two consecutive days, fits currently accepted criteria for first winter mongolicus. I spoke to several local gull enthusiasts about it (showing them these pictures etc)and it certainly is the type of bird they are identifying as mongolicus.

Note the already worn coverts and tertials, consistent with a bird that hatched somewhat earlier than the more Northerly Vega Gull.

Striking, contrasting plumage evident in flight. Note the very black tail band contrasting with the white rump; also, it has a very contrasting pattern on the inner primaries (P1-4), with pale lozenges on the outer webs and dark arrowheads at the tip.

Rather cachinnans-like plumage tones and patterns, especially the silvery base colour and light markings on the second generation scapulars. The head and body have a white ground colour, but with greyish streaks