Vega gull

The Vega gull is similar to the herring gull but is slightly darker grey above. The head of the Vega gull is heavily streaked with brown in winter, especially on the back and sides of the neck forming a collar. The legs are usually bright pink. First- and second-winter Vega gulls are darker than the similar Mongolian gull, notably on the crown of the head where Mongolian gulls even in first- and second-winter are a bit paler. Almost the full body of first- and second-winter Vega gulls displays darker brown flecks and streaks. Adult Vega gulls in winter can often be mistaken for the very similar-looking slaty-backed gull (L. schistisagus) and the western gull (L. occidentalis), but the Vega gull's gray is lighter than the two similar species. Eye colour is variable but tends to be dark with a red orbital ring. The bill is yellow with a red spot except for first- and second-winter gulls where the bill can be almost entirely dark gray/black, with the gray portion shrinking until it reaches maturity.

Vega gulls in the northwestern part of their breeding range are paler above. They are sometimes considered to be a separate subspecies named Birula's gull (Larus vegae birulai).

Adult Mongolian gulls swimming on Lake Baikal

The back and wings of the Mongolian gull vary in colour. They are often medium grey similar to Birula's gull but can be much darker. The head of the Mongolian gull is mainly white all year round with only faint winter streaking. The legs are usually pink and the eye is usually pale with a red orbital ring. The bill is yellow with a large red spot and often with dark markings in first-, second- and third-year gulls. First- and second-winter Mongolian gulls have heavy brown/gray streaking and flecking over most of body and wings, much like the Vega gull, but not as dark.