Difficult to separate from Yellow-legged Gulls and Herring Gulls without a careful appraisal of plumage characters. Candidate birds may draw attention by slender-billed, long-legged, and slim appearance. Flattened crown, rather small dark eyes, and usually unstreaked head are also useful characters. Wingtip (primary) feathers in adults have long tongues of white that penetrate into the black tips. Juveniles have prominent pale underwings. Breeds and winters predominantly on inland water bodies with some movement toward coasts in winter.