The Allure of the Ivory Gull
By Gerrit Vyn
January 15, 2009
Who would have thought 25 years ago that the Ivory Gull might soon face extinction caused by human activities? If ever a bird existed whose habits seemed to render it immune to our destructive effects on the environment, surely it was this one. The Ivory Gull nests as far north as any bird in the world, often laying its eggs on nunataks—sheer mountain peaks surrounded by glacial ice. During the frigid Arctic winter, it moves south just far enough to escape the complete darkness cast for months nearer the pole. In the company of ice, wind, and polar bears, the ghostly Ivory Gull plies the edges of twilight frozen seas where few people venture.
Today it is all too clear that close proximity to humans and an industrialized society is not a prerequisite for suffering their ill effects. Some of the most remote regions of our planet, those nearest the poles, are among the first to be facing profound, climate-driven ecological changes. The Ivory Gull’s year-round association with sea ice and its position at the top of the Arctic food web make it especially susceptible to these changes and to environmental pollution swept north by prevailing winds and ocean currents. Recent surveys in Canada revealed an 80 to 85 percent population decline in the species’ breeding population there since the 1980s, raising concern for the survival of the species and rumors of its imminent demise. Researchers are scrambling to understand the ecology and status of this enigmatic and exceptionally difficult to study bird and answer the question that everyone has been asking: What is really happening to the Ivory Gull? Although it seems unlikely that any one factor is driving the bird’s apparent decline, scientists are slowly assembling the pieces, and human activities are certainly implicated.
The Ivory Gull was discovered in 1609 by English explorer and whaler Jonas Poole. Despite its early discovery, the bird’s northern haunts and its rarity away from its scattered breeding colonies have left it one of the world’s most poorly understood seabirds. Today, researchers face enormous financial and logistical obstacles in their efforts to find and study the species in its remote breeding colonies in Arctic Canada, Greenland, Svalbard (Norway), and Russia. Studying the winter ecology of the Ivory Gull in the icy North Atlantic and Bering Sea has not yet even been attempted in earnest, thus baseline data on the bird’s past and present population sizes, migratory behavior, and winter foraging habits are still largely unavailable. This poses significant problems for researchers as they try to nail down the species’ population status and trends. Finding and counting all of the Ivory Gulls in any given year is simply impossible.
In the Canadian Arctic, where relatively good historical data on Ivory Gull populations does exist, thorough systematic surveys are now being accomplished for the species on a regular basis. As a result, scientists have found that the breeding population of the Ivory Gull in Canada has plummeted by as much as 85 percent since the early 1980s. Once numbering an estimated 2,450 breeding pairs, only 500 or fewer are known to exist there today. Breeding colonies that traditionally held hundreds of pairs from year to year are now abandoned; the few remaining colonies are steadily declining or harbor just a few isolated pairs. The only Canadian Ivory Gull populations that researchers believe have any chance of surviving are those on northeastern Ellesmere Island, where a number of previously unknown colonies have recently been discovered, and on tiny Seymour Island, which has a colony of 60 to 70 pairs at the species’ westernmost breeding location.
What scientists cannot say for certain is whether some birds have moved elsewhere to breed or whether the population is simply dying off. Although the latter is considered the most likely scenario by most scientists who study the species, the Ivory Gull is genetically similar across its entire world range, suggesting that dispersal and recolonization of other breeding sites may be a regular part of this species’ life history. Recent satellite tracking of birds in Greenland and Norway confirms that individuals do occasionally breed in different colonies from year to year, but also that birds typically return to the same general areas to breed.
As encouraging as the discovery of new colonies on Ellesmere Island was in 2006, though, the nest-associated vegetation at the sites suggests that the colonies have existed there for a long time and are probably not made up of individuals from other areas, as many researchers had hoped.
In the Old World, where consistent historical data are lacking and the bulk of the world’s remaining Ivory Gulls breed, population trends are still unknown and of great concern to scientists. Researchers launched an annual survey in 2006 in Svalbard, Norway, but they have yet to detect any definitive recent population trends. Preliminary findings suggest that the species has declined over the last century and that the breeding population there was previously overestimated. Researchers now estimate that only 350 to 650 pairs remain there. Another ominous discovery is that many of the large historical colonies previously known in the region—particularly those on flat ground—are gone, and other colonies have fewer individuals than they did before.
Without question, the Ivory Gull’s stronghold lies on the remote islands scattered in the Barents and Kara seas in the Russian Arctic, where 85 percent or more of the bird’s world population now breeds. Long-term population trends for this region are completely unknown, and although populations at several key colonies appear to be stable, populations at other colonies fluctuate widely from year to year. In some cases, colonies hold as few as a couple dozen pairs one year and many hundreds the next. Whether birds that nest in these colonies are just not breeding in some years or whether they are breeding elsewhere is still unknown. In all, colonies in Russia may support 4,500 or more breeding pairs.
Although researchers hope that the Ivory Gull’s global population is still hanging on, many fear that the species’ fate in Canada is a harbinger of things to come elsewhere. Factors known to have a negative effect on Ivory Gulls, such as native hunting and oiling at sea in Atlantic Canada (where 300,000 Thick-billed Murres and Dovekies perish each winter), have been considered in its decline, but they do not account for the precipitous, range-wide drop in the Canadian population. So what is happening? The first and most obvious suspect is global climate change.
Like the polar bear, the Ivory Gull’s existence is inextricably linked to the Arctic ice. The genus Pagophila, of which the Ivory Gull is the sole representative, means ice-loving. The species lives its life at the top of a complex ice-associated food web and has evolved to fill a niche in one of the harshest environments on earth. It makes its living as an opportunistic feeder, following ice edges and leads, where it preys on polar cod, lantern fish, and crustaceans such as cephalopods. These organisms congregate under the ice and flourish along ice edges where summer sunlight penetrates and fuels the growth of rich aquatic communities. Ivory Gulls also scavenge the ice, feeding on polar bear kills and on the placenta and feces of marine mammals. In winter, thousands of Ivory Gulls congregate in the North Atlantic, where seals give birth to their young on the ice. In summer, gull breeding colonies are seldom far from the ice. Observers at several colonies in Russia have noted that few gulls return to nest in years when little ice is present.
Climate change is certainly the greatest long-term threat to the Ivory Gull. As temperatures rise in the Arctic—at a rate three to five times faster than the average in other parts of the world—the ice and the biological communities associated with it are changing. How these changes are affecting Ivory Gulls is not yet known, but scientists suspect that the Ivory Gull is having more difficulty finding food now. But why these gulls seem to be abandoning areas that still appear to have excellent habitat is a mystery and suggests that something else is contributing to the species’ decline.
In the fall of 2008, researchers in Tromsø, Norway, announced the results of a study that gave the Ivory Gull a dubious distinction. In a sample of 35 Ivory Gull eggs collected in Svalbard, Russia’s Franz Josef Land, and Severnaya Zemlya, researchers detected the highest concentrations of the banned industrial pollutants PCB and DDT ever recorded in an Arctic seabird—and Arctic seabirds are among the most contaminated birds in the world. Prevailing winds and ocean currents deposit these long-lasting, human-made, organic pollutants north where they work their way up the food web and accumulate in the fatty tissue of animals. As a top predator, and one that feeds extensively on fatty fish such as polar cod and the fat-laden remains of marine mammals, the Ivory Gull is accumulating these chemicals at record rates—concentrations greater than those shown to have a negative effect on the breeding success and adult survival rates of another northern species, the Glaucous Gull. A 2001 United Nations convention outlawed most uses of these chemicals after they were detected in the breast milk of Inuit women and polar bears. Since then, the levels of these chemicals have been falling in the Arctic, so no one knows why their levels are so much higher in Ivory Gulls than other birds.
In a similar finding in the Canadian Arctic, Ivory Gull eggs collected on Seymour Island had mercury concentrations among the highest ever recorded for an Arctic seabird—levels definitely high enough to interfere with reproduction.
According to Hallvard Strøm, a leading Norwegian researcher who studies Ivory Gulls in Svalbard, the pollutants alone are probably not responsible for the Ivory Gulls decline, but they may act in concert with other stresses imposed by global warming and changing sea ice conditions. The combination may be too much for the species to handle. Strøm explains that toxic pollutants generally wind up in a bird’s fat, where they are largely benign, but in periods when food demands are not being adequately met—as may well be the case as the ecology of Arctic ecosystems and ice conditions change—the fat is metabolized and the toxic chemicals enter the bloodstream, causing problems for the bird. Food demands are particularly high when the birds are reproducing and trying to feed their young, and also during migration and winter, when many birds may be perishing.
Strøm also speculates that losing the winter ice shelf along eastern Greenland could pose another obstacle to the species’ long-term survival. Satellite tracking in 2008 discovered that the majority of the Old World Ivory Gull population migrates along eastern Greenland to wintering areas in the Davis Strait between Greenland and Canada. Others migrate north of Russia to wintering areas in the Bering Sea. Researchers previously thought that these birds wintered in the Barents and Greenland seas.
Ironically, some of the species most removed from our daily lives and our industrialized society may be the ones most at risk as the climate and ecology of our planet change. Facing far greater threats than the damming of a river or the felling of a forest, species today face a world of unknowns. Our changing climate and persistent pollution have created problems long in the making and difficult to fix—problems that are dismantling the very ecological fabric of entire biological communities. For the Ivory Gull, scientists foresee few hopeful scenarios for the species’ long-term survival. The bird is literally sitting on top of a melting world with no place else to go.