Ivory Gulls Mysteriously Disappear
Colonies of ivory gulls nesting on gravel plateaus of northwestern Baffin Island used to be so thick that local Inuit mistook the birds from a distance for patches of snow.
Surveys in the last few years have recorded a precipitous decline in birds breeding on the Island, and abandonment of 13 historic nesting sites.
In 2006, a thorough search of gull habitat on Baffin Island found only one pair.
While Baffin Island's Brodeur Peninsula has undergone the most dramatic drop in ivory gulls, that's not the only recent loss. Scientists conclude that ivory gulls nesting in Canada have decreased in number by 70 to 80 percent since the early 1980s. The 2006 census for the country was 842 individuals. This information prompted COSEWIC (Committee on the Status of Endangered Wildlife in Canada) to change the bird's status in 2006 from special concern to endangered. Ivory gulls, Pagophila eburnean, stand apart from all other seabirds as the lone species in the Pagophila genus.
The graceful, white bird only nests north of the Arctic Circle and even in winter stays along the edges of sea ice. While they also breed in other high Arctic countries, ivory gulls are rare. Their global status is unknown, although declines are suspected in Norway. Research in Canada presents some of the most detailed assessment of their population dynamics.
Other Canadian nesting sites are on remote mountain peaks, called nunataks, sticking out of the glaciers covering southern Ellesmere Island and Devon Island in Canada's Nunavut Territory. The birds select these cliffs to avoid egg-eating Arctic foxes and lemmings.
Out of 65 known breeding colony locations in Canada used in the last three decades, 26 were never occupied from 2002 to 2006. The size of active colonies has also shrunk, with the number of birds observed nesting at each site dropping from an average of 68 before the 1990s to nine birds since 2002.
If the current rate of population decline continues on Ellesmere and Devon Islands, scientific projections based on documented colony extinctions show that the fate of ivory gulls there will replay the recent outcome on Baffin Island. Within ten years, there'll be too few birds to maintain breeding populations.
Another Canadian colony exists farther west on tiny, low-lying Seymour Island. The decline here has been relatively gradual, averaging 2.7 percent annually from 1974 to 2006. This one site has a better chance than any other of supporting ivory gulls over the long term. Scientists at Environment Canada warn though, that unless things change, the gulls will soon be extirpated from most of their breeding range in the country.
The reasons for the dwindling of ivory gull populations haven't been confirmed, but researchers have speculated on several possible causes. For one, ivory gulls might be yet another animal struggling with rising Arctic temperatures.
Accumulating pollutants could be also be harming the gulls. Eggs collected recently on Seymour Island contained unusually high mercury concentrations, toxic enough to interfere with reproduction.
The abandonment of Brodeur Peninsula by ivory gulls coincides with a sudden flurry of activity by prospectors exploring for diamonds. Within a few years most of the Peninsula has been covered in claim stakes and prospecting permits. Whether the accompanying disturbances of exploration drilling, a field camp and surveys from planes and helicopters have driven away the gulls is unknown.
Gregory J. Robertson, H. Grant Gilchrist and Mark L. Mallory. 2007. Colony Dynamics and Persistence of Ivory Gull Breeding in Canada. Avian Conservation and Ecology. 2(2): 8.
Committee on the Status of Endangered Wildlife in Canada. 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.