American Herring Gull (smithsonianus)

(last update: October 30, 2015)

Coordinators:
Amar Ayyash (US)
Bruce Mactavish (Canada)
Dave Brown (Canada)
Mars Muusse (Netherlands)

Slaty-backed Gull (schistisagus) 4th cycle (5CY), February 21 2014, Choshi, Chiba, Japan. Picture: Shiroto.

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Overall adult-like bird with white tail, large mirror on P10 and adult-like upperparts. Only feature is much black on bill, probably indicating 5CY age, but advanced 4CY hard to exclude.