Adult winter
Mongolian Gull Larus cachinnans(?) mongolicus
November 30th 2004 Choshi Chiba Japan.

Note the sparse, thin head streaking. The primary molt is about to finish earlier than the majorities of Vega Gull. The general structure tends to look longish and squarish. It reminded me of  this 1st winter bird.

Black markings are seen on the both mandibles. The red spot does not reach the upper edge of lower mandible.

The Mongolian Gull in the foreground
with a typical Vega Gull in the back ground.

Compare their head streaking.

Note the black marking on P4, and relatively extensive black on P6-8.

The neck comparatively tends to show more obvious S-shape, presumably, because of  its slight longer length.

The legs are obviously paler pink than most Vega Gulls. This characteristic is often seen in 1st winter birds as well. And the tibias might tend to be slightly barer than Vega Gulls.

Vega Gulls Larus vegae on the same date for comparison.

Here is typical molt timing of  Vega Gull. P8 or P7 are still the longest replaced primary in these average Vega Gulls, though of course some are later or advanced than these individuals.

A 'taimirensis' on the same date. Note the very late molt-timing. The other 'taimyrensis' on the same date also showed similar molt-timing.