Ivory Gull Life History

Habitat

Habitat Oceans

Ivory Gulls inhabit the farthest northern reaches of the High Arctic, frequenting pack ice and the ice edges, especially around islands or headlands. They are seldom found far from sea ice, including drift ice, ice pans, and icebergs as well as polynyas (patches of open water within the pack ice). Ivory Gulls are remarkably flexible in their nest sites, using islands, cliffs, high mountains well inland (over 6,000 feet elevation, as much as 40 miles from the sea), nunataks (stony outcroppings within glaciers), flat islands, beaches, and even floating blocks of ice. After breeding, they sometimes appear on beaches near human settlements in the far north. They remain in the Arctic throughout the dark winter months, within pack ice or near its edges, sometimes near mammals such as seals or polar bears.

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Food

Food Fish

Ivory Gulls eat fish and marine invertebrates found around pack ice. They also scavenge at carcasses left by human hunters and polar bears, including whales, seals, walrus, other marine mammals, and birds. They sometimes follow whales or polar bears, and they also consume the placenta and feces of mammals. Like other gulls, Ivory Gulls steal food from other gulls (including species larger than themselves) and other seabirds, including murres. Their foraging techniques are varied. At sea, they hover over prey-rich areas, then dip down to the water to seize prey in the bill or sometimes plunge into the water in pursuit. They wade at water’s edge to pick prey from ice or beaches, and they are bold and even aggressive foragers on carrion, sometimes challenging larger birds for food. They feed during darkness as well as during daylight. Other foods include larvae of midges, squid, mollusks, small crustaceans (isopods, copepods, amphipods, euphausiids), sea squirts (tunicates), bristleworms (polychaetes), lanternfishes, walleye pollock, arctic cod, Dovekie, and lemmings. One study noted brown algae and cinquefoil seeds in the diet. In settlements, they consume carrion and garbage readily.

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Nesting

Nest Placement

Nest Ground

Male and female construct the nest together, set in predator-free sites such as cliffs, ridges, mountains, islands, beaches, and even on floating ice.

Nest Description

Nests on ice incorporate few materials, but most nests are made of mosses, grasses, seaweeds, lichen, flowering plants, bits of driftwood, feathers, down, and mud. Nest dimensions vary widely; nests may be 9–24 inches across and 5–9 inches tall, with interior cup about 6 inches across and 1 inch deep.

Nesting Facts

Clutch Size:1-3 eggs
Egg Description:

Dark to pale brown with variable amount of dark spotting and blotching.

Condition at Hatching:

Alert and mobile, covered with white down.

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Behavior

Behavior Ground Forager

In late winter or spring, Ivory Gulls gather near nesting areas or nearby coastal sites. They court at this season much like other gull species, giving “long calls” while bowing and partly opening the wings, often in small groups. Males courting females offer them small stones and make head-tossing displays and softer calls. Receptive females respond with head tossing and may rub the head against a male’s breast, to which he may respond with regurgitation of a meal for his prospective mate. They nest monogamously in small, loose colonies, sometimes near other birds such as Brant. Both sexes share nest-building, incubation, and chick-feeding duties, and they display throughout these stages, giving long calls, landing calls, and meeting calls when interacting at the nest site, especially when relieving their mate during incubation. Other Ivory Gulls, probably males, often attempt to interrupt courtship—interposing themselves between the pair or stealing regurgitated food—and some attempt to mount incubating females and males. Nonbreeding birds and “off-duty” adults sometimes gather in small groups around freshwater ponds to bathe, preen, and rest. The young disperse to sea soon after fledging. Ivory Gulls tend to be solitary or in small groups during the nonbreeding months.

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Conservation

Conservation Restricted Range

Little is known about Ivory Gull populations because of the remoteness of their breeding and wintering areas. Partners in Flight estimates a global breeding population of 45,000, rates the species a 16 out of 20 on the Continental Concern Score, and includes it on the Yellow Watch List for birds with restricted ranges. Given the Ivory Gull's extreme northern range and reliance on sea ice, the species' chief conservation concern is the impact of climate change on its habitat and food resources. Several studies have detected high levels of pesticides and heavy metals in Ivory Gull eggs and organs. (Ocean currents tend to carry these substances northward and concentrate them in the Arctic, making pollution a problem despite this species' extremely remote habitat.)

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Credits

Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA.

Lutmerding, J. A. and A. S. Love. (2019). Longevity records of North American birds. Version 1019 Patuxent Wildlife Research Center, Bird Banding Laboratory 2019.

Mallory, Mark L., Iain J. Stenhouse, H. Grant Gilchrist, Gregory J. Robertson, J. Christopher Haney and Stewart D. Macdonald. (2008). Ivory Gull (Pagophila eburnea), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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