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 time without food, but also allows them to transport nutrient-rich foods back to their chicks from distant sources. Like other species, the fork-tailed storm petrel spend most of their time out at sea and will only return to land to breed around late March to early April. To avoid predation and harassment by gulls, these birds will only enter the colony at night and depart before sunrise. The fork-tailed storm petrel builds its nest in rock crevices or small burrows on isolated islands. Courtship consists of vocalizations and aerial displays, often lasting for several weeks. Once established, pairs will remain