| Ivory gull | |
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Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Charadriiformes |
| Family: | Laridae |
| Genus: | Pagophila Kaup, 1829 |
| Species: | P. eburnea |
| Binomial name | |
| Pagophila eburnea (Phipps, 1774) | |
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| Synonyms | |
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Theivory gull (Pagophila eburnea) is a smallgull, theonly species in the genusPagophila. It breeds in the highArctic and has a circumpolar distribution throughGreenland, northernmostNorth America, andEurasia.
The ivory gull was initially described byConstantine Phipps, 2nd Baron Mulgrave in 1774 asLarus eburneus from a specimen collected onSpitsbergen during his1773 expedition towards the North Pole.[2]Johann Jakob Kaup later recognized the unique traits of the ivory gull and gave it a monotypic genus,Pagophila, in 1829.[2]Johan Ernst Gunnerus later gave the species a new specific name,Pagophila alba.[2][dubious –discuss] The genus namePagophila is fromAncient Greekpagos, "sea-ice", andphilos, "-loving", and specificeburnea isLatin for "ivory-coloured", fromebur, "ivory".[3] Today some authors consider the ivory gull not deserving of its monotypic genus, instead choosing to merge it, along with the other monotypic gulls, back intoLarus.[2] However, most authors have not chosen to do so. The ivory gull has no subspecies.[2] No fossil members of this genus are known.[4]
This gull has traditionally been believed to be most closely related to either thekittiwakes,Sabine's gull, orRoss's gull.[2] It differs anatomically from the other genera by having a relatively shorttarsometatarsus, a narroweros pubis, and potentially more flexibility in skull kinetic structure.[2] Structurally, it is most similar to the kittiwakes; however, recent genetic analysis based onmtDNA sequences shows that Sabine's gull is the ivory gull's closest relative, followed by the kittiwakes, with Ross's gull andswallow-tailed gull sharing aclade with these species.[2][5]Pagophila is maintained as a unique genus because of the bird's morphological, behavioral and ecological differences from these species.[2]
Colloquial names from Newfoundland include slob gull (from "slob", a local name for drift ice) and ice partridge, from a vague resemblance to aptarmigan.[6]
This species is easy to identify. At approximately 43 centimetres (17 in), it has a different, morepigeon-like shape than theLarus gulls, but the adult has completely whiteplumage, lacking the grey back of other gulls. The thickbill is blue with a yellow tip, and the legs are black. The bill is tipped with red, and the eyes have a fleshy, bright red eye-ring in the breeding season. Its flight callcry is a harsh, tern-likekeeeer. It has many other vocalizations, including a warbling "fox-call" that indicates potential predators such as an Arctic fox, polar bear, Glaucous Gull or human near a nest, a "long-call" given with wrists out, elongated neck and downward-pointed bill, given in elaborate display to other Ivories during breeding, and a plaintive begging call given in courtship by females to males, accompanied by head-tossing. 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.[2]
Measurements:[7]
In North America, it only breeds in theCanadianArctic.[4]Seymour Island,Nunavut is home to the largest known breeding colony, whileEllesmere,Devon,Cornwallis, and northBaffin islands are known locations of breeding colonies.[4] It is believed that there are other small breeding colonies of less than six birds that are still undiscovered.[4] There are no records of the ivory gull breeding inAlaska.[4]
During the winter, ivory gulls live nearpolynyas, or a large area of open water surrounded by sea ice.[4] 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 theLabrador Sea toDavis Strait that is bordered byLabrador and southwestern Greenland.[4] Wintering gulls are often seen on the eastern coasts ofNewfoundland and Labrador and occasionally appear on the north shore of theGulf of St. Lawrence and the interior of Labrador.[4] It also winters from October through June in theBering Sea andChukchi Seas.[4] It is most widespread throughout the polynyas and pack ice of the Bering Sea.[4] 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, as well as TheBritish Isles, with most records from late November through early March.[4] Juveniles tend to wander further from the Arctic than adults.[4]
Ivory gullsmigrate 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 takesfish andcrustaceans,rodents,eggs and small chicks but is also an opportunistscavenger, often found onseal orporpoise corpses. It has been known to followpolar bears and other predators to feed on the remains of their kills.
The ivory gull breeds on Arcticcoasts and cliffs, laying one to three oliveeggs in a groundnest lined withmoss,lichens, or seaweed.
In 2012 the total population of ivory gulls was estimated to be between 19,000 and 27,000 individuals.[1] The majority of these were in Russia with 2,500–10,000 along the Arctic coastline, 4,000 on theSevernaya Zemlya archipelago[8] and 8,000 onFranz Josef Land andVictoria Island. There were also estimated to be around 4,000 individuals inGreenland[9] and in the years 2002–03, 500–700 were recorded in Canada.[1] Examination of data collected on an icebreaker plying between Greenland and Svalbard between 1988 and 2014, by Claude Joiris of theRoyal Belgian Institute of Natural Sciences, found a sevenfold fall in ivory gull numbers after 2007.[10] The species is rapidly declining in Canada, while in other parts of its range its population is poorly known. The Canadian population in the early 2000s were approximately 80% lower than in the 1980s.[10]
Illegal hunting may be one of the causes of the decline in the Canadian population, and a second cause may be the decline in sea ice. Ivory gulls breed near to sea ice and the loss may make it difficult to feed their chicks.[10][11]
The species is classified by theInternational Union for Conservation of Nature as "Near Threatened".[1]
An ivory gull is the inspiration for the eponymous carving inHolling C. Holling's classicNewbery Medal-winning children's book,Seabird.
{{cite journal}}: CS1 maint: DOI inactive as of November 2024 (link)
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