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
Black-tailed gull it has been rebuilt several times since) at which the black-tailed gull, is seen as a messenger of the goddess of the fishery. For over 700 years, the species has enjoyed reverence, feeding and protection from the local population. As a result, every summer, over 40,000 black-tailed gulls nest and raise their young in the grounds of the shrine and the surrounding island, which has been designated a National Natural Monument by the government of Japan. The gulls are very tame and are a popular local tourist attraction. Around 5,000 birds also nest at Fumi-shima in Shimane Prefecture near Izumo