L 37-44 cm (excl. ad. summer tail projections 5- 8½), WS 108-118 cm. Breeds on tundra, coastal moors and barren islands, locally in loose colony; winters mainly S of the Equator. In Britain fairly common locally in N Scotland. Nest a shallow depression. Often keeps watch from top of island or a moorland ridge.
IDENTIFICATION: Like a dark gull with pointed wings and fast, flexible, almost falcon-like flight. At closer range, light primary patches and on adult half-length, pointed tail projections. In flight, appears to be of Kittiwake size. Wings long and fairly narrow, ‘hand’ pointed; width of ‘arm’ appears equal to or slightly less than distance from rear edge of wing to tip of tail (projections disregarded). Flight lighter than Pomarine’s, but beware, may at times show some weightiness; in strong winds Arctic recalls a Kittiwake in lightness, quick wingbeats and sudden lunges, whereas Pomarine is decidedly heavier and more steady, like a large gull. Bill a little finer than on Pomarine. Plumages much as for Pomarine - thus large variation - but note the following distinctions: dark cap of adult less black, does not solidly surround gape, and always excludes a small light patch above base of bill; if breast-band present, usually a dark ill-defined shade, not coarsely patterned; palest juveniles lighter than Pomarine, have contrasting light head and neck (finely streaked; discernible at close range) and often belly, too. Darkest juveniles extremely similar to darkest Pomarine, most reliably identified by bill size, tail shape and overall proportions; note also pointed central tail-feathers projecting 1-3 cm, forming tiny ‘double point’ at rear of tail, primary coverts below lacking pale base (exceptions: 1 out of 20) and bill generally looking dark, not strikingly pale-based (tendency to paler base hardly visible beyond 150 m).
VOICE: Most often heard is a nasal, mewing ‘eh-glow’, repeated a few times in display. Alarm a short ‘pjew!’.