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
Fork-tailed storm petrel their tail. The fork-tailed storm petrel is a part of the tubenose order Procellariformes and family Hydrobatidae. The genus "Oceanodroma" arises from Ancient Greek "okeanos dromos", meaning "ocean runner", reflecting the storm petrel's distinct foraging style. Their specific name "furcata" is Latin for branched or forked, derived from "furcatus", referring to their characteristic forked tail. 2 subspecies are recognized: The major differences between the two subspecies are slight size and plumage differences, where southern populations appear somewhat smaller and darker. Southern populations also begin and end the breeding season earlier than their northern counterparts. However, no molecular genetic analysis has