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
Belcher's gull scrape in the sand or among rocks near the high tide line. There are usually three eggs averaging , pale blotched with dark olive markings. Belcher's gull is estimated to have a total population of under ten thousand individuals and an estimated distribution range of . Persecution of this bird by humans has diminished and its population is thought to be increasing. For these reasons, despite its small total population size and limited range, the International Union for Conservation of Nature considers it to be of "least concern". Belcher's gull Belcher's gull ("Larus belcheri"), also known as the band-tailed gull,