Very similar to Herring Gull, and not always possible to identify with certainty. Generally thicker neck, rounder head and longer wings than Herring Gull. Adults: Silvery upperparts, bright yellow legs (beware that it is not uncommon for Herring Gull to have yellow legs!), and more black and less white in wing-tips. Bill heavier than H.G. with markedly curved tip. Orbital ring red, not orange. Big, red gonys spot, often extending to upper mandible. Marked gonys angle. Primary feather P5 (counted from innermost feather in gulls) usually with broad, black band. In winter plumage head is less streaked than in H.G., and often completely white. Immatures first winter: Pale belly and head. Dark underwings with blotchy markings. Only vague pale window of inner primaries, and well defined, wedge-shaped tail-band. Dark base of bill. For a detailed account of all plumages see Gull Research.

Voice more nasal than Herring Gull, but ID by sound difficult.

Wikipedia: map (se also Xeno-canto below)

Birdlife ecology

Observation.org Latest observations

Video IBC

Image search Flickr NB! May give other species

Sound search at Xeno-canto

Featherbase