the ivory gull pagophila eburnea is a small gull , the only species in its genus .
it breeds in the high arctic and has a circumpolar distribution through greenland , northernmost north america , and eurasia .
the ivory gull was initially described by constantine phipps , 2nd baron mulgrave in 1774 as larus eburneus from a specimen collected on spitsbergen .
johann jakob kaup later recognized the unique traits of the ivory gull and gave it a monotypic genus , pagophila , in 1829. johan ernst gunnerus later gave the species a new specific name , pagophila alba .
today some authors consider the ivory gull not deserving of its monotypic genus , instead to choosing to merge it , along with the other monotypic gulls , back into larus .
however , most authors have not chosen to do so .
the ivory gull has no subspecies .
no fossil members of this genus are known .
this gull is traditionally believed to be most closely related to either the kittiwakes , sabine's gull , or ross's gull .
it differs anatomically from the other genera by having a relatively short tarsometatarsus , a 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 birds morphological , behavioral and ecological differences from these species .
this species is easy to identify .
at 43 cm (17 in), it has a different , more pigeon-like shape than the larus gulls , but the adult has completely white plumage , lacking the grey back of other gulls .
the thick bill is blue with a yellow tip , and the legs are black .
its cry is a harsh eeeer .
young birds have a dusky face and variable amounts of black flecking in the wings and tail .
the juveniles take two years to attain full adult plumage .
there are no differences in appearance across the species geographic range .
in north america , it only breeds in the canadian arctic .
seymour island , nunavut is home to the largest known breeding colony , while ellesmere , devon , cornwallis , and north baffin islands are known locations of breeding colonies .
it is believed that there are other small breeding colonies of less than six birds that are still undiscovered .
there are no records of the ivory gull breeding in alaska .
during the winter , ivory gulls live near polynyas , or a large area of open water surrounded by sea ice .
north american birds , along with some from greenland and europe , winter along the 2000 km of ice edge stretching between 50 and 64 n from the labrador sea to davis strait that is bordered by labrador and southwestern greenland .
wintering gulls are often seen on the eastern coasts of newfoundland and labrador and occasionally appear on the north shore of the gulf of st .
lawrence and the interior of labrador .
it also winters from october through june in the bering sea and chukchi seas .
it is most widespread throughout the polynyas and pack ice of the bering sea .
it is also vagrant throughout coastal canada and the northeastern united states , though records of individuals as far south as california and georgia have been reported , with most records from late november through early march .
juveniles tend to wander further from the arctic than adults .
it migrates only short distances south in autumn , most of the population wintering in northern latitudes at the edge of the pack ice , although some birds reach more temperate areas .
it takes fish and crustaceans , rodents , eggs and small chicks but is also an opportunist scavenger , often found on seal or porpoise corpses .
it has been known to follow polar bears and other predators to feed on the remains of their kills .
ivory gull breeds on arctic coasts and cliffs , laying one to three olive eggs in a ground nest lined with moss , lichens , or seaweed .
