Digiscoped 28 Dec 2011 at Lake Loveland, Larimer County, Colorado (USA). Field marks indicating Vega Gull, Larus vegae vegae, include darker gray mantle, contrasting with wide white tertial and scapular crescents, faintly-streaked crown and hindneck, appearance of a dark eye, trace of a crimson-red orbital, and bubble-gum-pink legs.
Vega Gulls breed along the north coast of Siberia and winter in the western Pacific coast (e.g. Japan). The gray-scale of the adult mantle varies geographically, with some populations pale (like L. thayeri??) and some darker (like L. californicus??); darkest gray birds apparently are found at the western and eastern extremes of the breeding range, including St. Lawrence Island, Alaska. Records of Vega Gull in Colorado are all currently considered hypothetical. This bird was not accepted as Vega Gull by the Colorado Bird Records Committee.
Click on an image to enlarge. Other species shown in these photos include American Herring Gull (L. a. smithsonianus), Thayer's Gull (L. thayeri), Lesser Black-backed Gull (L. fuscus graellsi), and Ring-billed Gull (L. delawarensis).