As an inhabitant of Arctic ice flows and snow fields, the Ivory Gull endures some of the harshest conditions on the planet. Yet in 2006, recent changes in its environment suddenly pushed the world's only all white gull onto Canada's Endangered Species list. Rarely descending from the Arctic, a stray Ivory Gull always draws a crowd of bird watchers, even though the species invariably appears in the temperate zone during cold winter months.
The adult Ivory Gull is an immaculate white with coal black eyes and feet. The pale gray bill is tipped with pale yellow. The sexes appear the same. More likely to wander into our population centers, immature birds look like adults but with variable amounts of black on the face and dark spots and smudges scattered over the body. These medium-sized gulls grow to 17 inches long and weigh 1.4 pounds with a 37-inch wingspan.
The North American breeding range of the Ivory Gull is restricted to a few sites in Arctic Canada. One population of these gulls winters just south of Greenland in the Labrador Sea. Another population winters in the Bering and Chukchi Seas. Ivory Gulls concentrate where the ice meets the sea and at openings surrounded by sea ice called polynyas. Otherwise, the Ivory Gull breeds and winters at select locations around the Arctic Circle.
Always on or near the seam between ice and water, this seabird breeds in a variety of habitats: coastal cliffs, sometimes as far as 18 miles inland and as high as 3,000 feet; rocky mounds; flat, gravely fields; and even recently calved icebergs covered with rock and dirt. Polynyas, ice flows, and the edges of sea ice are vital at all times of the year. Pack ice is favored in deep winter. Snow and soft ice are both used by the Ivory Gull for digging roost holes, providing shelter from the cold Arctic winds.
The Ivory Gull burns a lot of calories in its Arctic environment and must feed ravenously to meet these energy demands. Prey is located by sight over the water, on ice flows, at ice edges, and on gravel fields. Foraging methods include dipping, snatching, pecking, scavenging, and plunge-diving. Where whales churn the ocean as they feed, this opportunistic seabird picks animal plankton from the water. At ice edges, especially in low light conditions, the Ivory Gull takes lanternfish and the abundant boreal armhook squid. Small pollock, cod, krill, and copepods are also important dietary components. In summer, lemmings and midge larvae are consumed. Taking advantage of the work of large predators, the Ivory Gull is also an aggressive and meticulous scavenger. It readily eats carrion and animal droppings, and even attacks injured polar bears.
In April and May, groups of Ivory Gulls perform courtship displays at colony sites. Pairs bond with ritual calls, head tosses, stone carrying, and ritual feedings. Monogamous pairs establish territories and build nests together on stony ledges, gravel beds, or piles of eroded rock. Excavated with the feet, the nest bowl is a slight depression lined with feathers, grasses, moss, and seaweed. Unattended eider nests are also sometimes used.
For 24 to 26 days, the pair incubates one or two eggs, colored in variable shades of brown or olive, and marked with streaks and splotches of gray, olive, and purple. The downy, pure white chicks can soon walk and hide when threatened, but require parental feeding and brooding. Young chicks appear to receive digested fish, while mature ones can swallow small fish whole. Ivory Gulls grow rapidly and fledge in about a month, making the entire breeding season as short as 60 days. Juvenile Ivory Gulls follow adults on migration, where they continue to beg for food.
Weather and the formation of sea ice heavily influence the Ivory Gull's migratory behavior. The Ivory Gull follows three distinct phases for spring and fall migration. In September, following the breeding season, the birds move to open seas where more productive feeding areas exist. In October, they shift easterly, to the edges of the growing ice flows. Finally, they turn south into the northwestern Atlantic Ocean. Spring migrants follow the receding ice and also use polynyas for staging. Ivory Gulls migrate by day or night, either alone or in groups of several dozen to hundreds.
COSEWIC 2006. "
COSEWIC assessment and update status report on the Ivory Gull (Pagophila eburnea) in Canada." Committee on the Status of Endangered Wildlife in Canada. Ottawa. 42 pages. Accessed 11 May, 2007.
Haney, J. C., and S. D. MacDonald. 1995. Ivory Gull (
Pagophila eburnea). In
The Birds of North America, No. 175 (A. Poole and F. Gill, Eds.). The Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington, D.C.
Sibley, David Allen.
The Sibley Guide to Birds. Alfred A. Knopf, New York. 2000.
