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 flycatcher and Canada. This flycatcher builds a shallow cup nest high in a shrub or short tree. Females normally lay two or three eggs. The fork-tailed flycatcher is white below, gray above, and has a black cap. Males sometimes show a yellow crown stripe. Males also have an extremely long forked tail, of even greater length than that of their cousin, the scissor-tailed flycatcher. Females have a somewhat shorter tail, while it is significantly shorter in juveniles. Males are in length; females, , including tail. They weigh only , much less than closely related kingbirds, which are half the total length