The Xeme is a small gull that 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 the breeding season. The bill is black in color and has a yellow tip. Young birds have a similar tricolored wing pattern, but the grey is replaced by brown, and the tail has a black terminal band. Juveniles take two years to attain full adult plumage.
Xeme breed in the Arctic and have a circumpolar distribution through northernmost North America and Eurasia. They migrate south in autumn; most of the population winters at sea in the Pacific off western South America in the cold waters of the Humboldt Current, while Greenland and eastern Canadian birds cross the Atlantic by way of the westernmost fringes of Europe to winter off southwest Africa in the cold waters of the Benguela Current. Occasionally individual xeme can be seen off other coasts such as the northeastern United States or further east in Europe, typically following autumn storms. These gulls are often seen inland in North America, Europe, and even Siberia, and have been said to exhibit "cross-continental migration" in addition to migration at sea. Xeme breed on coasts and tundra preferring swampy and moss areas with many lakes, tidal marshes, and shallow brackish pools. Outside of the breeding season, these birds are very pelagic using deep cold oceanic waters.
Xeme are social birds and spend most of their time out at sea. They feed by day in large flocks over the open ocean or follow the fishing boats to feast on fish discards. During the breeding season, xeme typically feed singly or in pairs taking a range of freshwater and terrestrial prey on the tundra. They communicate with each other vocally and have a very loud high-pitched and squeaking call.
Xeme arrive on their breeding grounds between late May and early June. They breed in colonies but may also nest as single pairs. The female lays 2 or 3 spotted olive-brown eggs in a ground nest lined with grass. The eggs are incubated by both parents during 23-25 days. The chicks hatch fully-developed; they are covered in down and are able to leave the nest soon after hatching. The parents lead them to an area near water when the young feed mostly themselves.
Xeme are not considered threatened at present, however, they suffer from climate change, water pollution, human disturbances, hunting, and egg collection.
According to the IUCN Red List, the total population size of the xeme is over 340,000 mature individuals. The European population consists of 1,100-2,100 pairs, which equates to 2,100-4,100 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.