Sabine's gull treated as comprising a monotypic genus; it is only placed within the genus "Larus" when the genus is enlarged. The black bill and notched tail are almost unique within the gulls, as they are shared only with the swallow-tailed gull of the Galapagos. On the basis of this the two species were often thought to be each other's closest relatives, a hypothesis ruled out by a number of behaviour and ecological differences. Mitochondrial DNA studies confirmed that they are not closely related, and the closest relative of the Sabine's gull is now thought to be the ivory gull, another Arctic
Iceland gull Iceland gull The Iceland gull ("Larus glaucoides") is a medium size gull which breeds in the Arctic regions of Canada and Greenland; although not in Iceland (as its name suggests), where it is only seen during winter. The genus name is from Latin "Larus" which appears to have referred to a gull or other large seabird. The specific "glaucoides" denotes its resemblance to "Larus glaucus", a synonym of "Larus hyperboreus", the glaucous gull; "-oides" is Ancient Greek and means "resembling". It is migratory, wintering from in the North Atlantic as far south as the British Isles and northernmost states of