Heuglin's Gull Larus heuglini
February 24th 2005 Choshi Chiba Japan
Of course the border between heuglini and 'taimyrensis' seems to be unclear. But at least this individual doesn't seem to have any wrong feature for heuglini.
Note the 8 black-marked primaries, P10-P3. And the P10 mirror is very small. Of course this extensive black would be caused by its age in some degree. But I feel this pattern fits heuglini well.
A 'taimyrensis' (right) with a Vega Gull on the samedate for comparison