Sabine's gull steals eggs from nesting colonies of Arctic terns. The Sabine's gull is a small gull, in length and weighing . The wings are long, thin and pointed with a span of between . The bill, which is black with a yellow tip, is around long. This species is easy to identify through its striking wing pattern. The adult has a pale grey back and wing coverts, black primary flight feathers and white secondaries. The white tail is forked. The male's hood darkens during breeding season. Young birds have a similar tricoloured wing pattern, but the grey is replaced by brown,
Sabine's gull species. The two species are thought to have separated around 2 million years ago, longer ago than most groups of gull species. Geographical variation is slight; birds from Alaska are slightly darker and perhaps bigger. Most authorities recognise no races, but a few recognise four based on size and mantle (back) colour. The Handbook of the Birds of the World recognises four subspecies. The nominate subspecies, "X. s. sabini", breeds from the Canadian Arctic to Greenland. "X. s. palaearctica" (Stegman, 1934) breeds from Spitsbergen to the Taymyr Peninsula in Russia, and "X. s. tschuktschorum" (Portenko, 1939) breeds on the Chukotskiy