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
Swallow-tailed gull chick takes its first flight at about 60–70 days old, and is fed by the adults until about 90 days, when it leaves the land, possibly with the adults, to live over the open seas. Population trends have not been estimated, but it is not thought to be threatened. The population was estimated to be about 35,000 individuals when it was last considered in 2004. Swallow-tailed gull The swallow-tailed gull ("Creagrus furcatus") is an equatorial seabird in the gull family, Laridae. It is the only species in the genus Creagrus, which derives from the Latin "Creagra" and the Greek "kreourgos"