Subspecies

Larus glaucoides thayeri (Thayer’s gull)

Larus glaucoides thayeri. Photo: (c) Guy Monty, some rights reserved (CC BY-NC-SA)

Thayer’s gull (Larus glaucoides thayeri) is a subspecies of the Iceland gull. It is a large gull native to North America that breeds in the Arctic islands of Canada and winters primarily on the Pacific coast, from southern Alaska to the Gulf of California, though there are also wintering populations on the Great Lakes and the upper Mississippi River. The species has occurred as a vagrant to Japan, Denmark, and other parts of western Europe.

— Wikipedia