Short-billed gull

Appearance

The short-billed gull is a small gull with a length 40–45 cm and a wingspan 100–120 cm. It is smaller than other gulls in the Common gull complex, with a shorter bill and longer wings. Its wings appear long and narrow in flight relative to its short body. In breeding plumage, adults have a white head, pale eyes surrounded by a red orbital skin, yellow legs and bill with not markings. In winter, the head is marked with brown mottling, the eye orbital skin becomes greyish and the bill becomes duller with a faint dark marking. In flight, the two outermost primary feathers have conspicuous white spots or "mirrors". Between p5 and p8, the primaries have white "tongue tips" which form a 'string of pearls' transitioning to the broad white trailing edge. p4 usually has a black markings in many birds. In comparison, common gulls have a larger bill and shorter wings. The wingtips of common gulls have more extensive black wingtips with smaller mirrors on p9-10, a narrower trailing edge, and typically lack black markings on p4 as well as the white tongue tip on p8.

Short-billed gulls take 3 years to attain breeding plumage. Juveniles are brownish overall with dark brown wingtips. They appear darker and more smudged on the head and neck, compared to the paler and finely-marked common gull, which more closely resembles Ring-billed gull at this stage. Many first-year birds retain juvenile plumage through the winter, but some grow greyish saddle feathers intermixed with juvenile feathers. The bill becomes pink at the base with a black tip by the first winter. Second-year birds resemble adults but may have brown wing covert feathers and black markings on the tertials, lacking white spots on the wingtips except the p10 mirror. Third-year birds are similar to adults but may have dark markings on primary coverts, secondaries, underwing and tail, with more extensive black on the wingtips.

Distribution

The short-billed gull breeds in colonies along coastal areas and inland wetlands, mainly in Alaska and Northwest Canada. Most birds winter along the Pacific coast down to the Sacramento Valley, and less frequently to Baja California, the Northern Rockies and Ontario. It is a very rare visitor to eastern North America and a vagrant to east Asia. There is one recent record of a short-billed gull in Europe, on the Azores in 2003.