"Mew Gull, although some authorities (rightly) split Mew Gull into three or even four;
Mew Gull, Larus canus brachyryhnchos of north-western North America,
Common Gull, Larus canus canus of Europe and
Kamtchatka Gull, Larus canus kamtschatschensis of the far east.
Sort of in between is Russian Common Gull, Larus canus heinei, a sort of intergrade between Larus canus canus (Common) and Larus canus kamtschatschensis (Kamtchatka)."-Mark Dennis