Ivory gull narrower os pubis, and potentially more flexibility in skull kinetic structure. Structurally, it is most similar to the kittiwakes; however, recent genetic analysis based on mtDNA sequences shows that Sabine's gull is the ivory gull's closest relative, followed by the kittiwakes, with Ross's gull and swallow-tailed gull sharing a clade with these species. "Pagophila" is maintained as a unique genus because of the bird’s morphological, behavioral and ecological differences from these species. Colloquial names from Newfoundland include slob gull (from "slob", a local name for drift ice) and ice partridge, from a vague resemblance to a ptarmigan. This species is
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