As the Arctic Warms, Hungry Polar Bears Are Eating More Seabirds—Wiping Out Colonies

One summer season day in 2024, a polar bear walked throughout the flat, wild shore of Spy Island, Alaska. Frequent Eiders nested there, with birds and eggs within the a whole bunch. By the tip of the day, virtually all of them have been gone.

“Once we arrived, it was very quiet,” says Kayla Shively, conservation ecologist on the Wildlife Conservation Society, which has been monitoring the colony for years. “No grownup females remained on the island. We began noticing scat, crushed eggshells, and bear tracks zigzagging from nest to nest.” Shively’s workforce had stumbled upon a rising risk to Arctic seabirds: hungry polar bears. 

Because the Arctic warms, polar bears are shedding the summer season sea ice the place they hunt seals, their main prey. That’s driving them onto land, the place they more and more forage for seabird eggs, nestlings, and typically adults. Whereas the conduct isn’t new, researchers are observing it extra typically within the Canadian Arctic, Svalbard, and Greenland in current many years. 

A new scientific paper, co-authored by Shively and printed in Polar Analysis this month, offers the primary report of large-scale bear-bird predation in Alaska, confirming that it’s taking place throughout the Arctic. 

On Alaska’s north coast, the shore is usually low tundra fronted by barrier islands within the Beaufort Sea. These islands are essential nesting grounds for seabirds, past the attain of conventional predators like Arctic foxes. Traditionally, polar bears not often appeared right here in summer season, however as sea ice has melted, their numbers have elevated sixfold up to now 20 years. Nests are notably weak to predation on these small islands, the place one or two polar bears can devastate a complete colony.

The paper studies on two colonies: Cooper Island’s Black Guillemots and Spy Island’s Frequent Eiders. 

Small and gravelly, Cooper Island is the long-time summer season residence of Mandt’s Black Guillemots, an Arctic subspecies. These birds initially nested underneath planks, ammo packing containers, and different particles left by the U.S. Navy following the Korean Battle. When ornithologist George Divoky, co-author of the examine, began observing the colony in 1975, polar bear predation was uncommon. However within the breeding seasons from 2008 by means of 2010, bears killed practically half of all nestlings. In 2011, researchers put bear-proof nest instances on the island, however ultimately, bears realized to interrupt them open, even submerging them in water to flush out grownup birds. In 2024 and 2025, bears brought on full reproductive failure within the colony. 

Farther east, on Spy Island, Pacific Common Eiders, additionally a subspecies, nest in driftwood, sparse vegetation, and low dune ridges. Females of this largest sea duck within the Northern Hemisphere spend the best proportion of time on their nests of any waterfowl, Shively says. Right here, too, studies of bear predation had been uncommon since surveys started within the Seventies. Then, in 2016 and 2017, bears destroyed 11 p.c of greater than 200 monitored nests. And that day in July 2024, a single bear destroyed 89 p.c of nests in lower than 24 hours. 

For these two species as a complete, the polar bear risk isn’t existential. Certainly, “most seabird species within the Arctic are nonetheless in comparatively good condition,” says Don Lyons, director of conservation science at Audubon’s Seabird Institute. “They’re not prone to extinction within the subsequent 50 years. However they’re going to face actual challenges, and will grow to be endangered in that timeframe.” 

Like predation from polar bears, a lot of these challenges are pushed by the local weather disaster. Sea ice loss is contributing to elevated storm surges, flooding, and shoreline erosion, shrinking nesting grounds for eiders. “In northern Alaska, that’s the best risk to Pacific Frequent Eiders,” says Shively. For guillemots, hotter waters imply fewer Arctic cod, their main meals—with the Cooper Island colony doubtless going through extinction within the close to future, as Divoky warned in a recent paper.

In comparison with these threats, polar bears could also be solely a short-term downside, however for an unlucky motive, says Andrew Derocher, a biologist on the College of Alberta. Elsewhere within the Arctic, bears are much less weak to sea ice decline, and are studying to hunt species like reindeer and walrus. However within the southern Beaufort Sea, he says, “the inhabitants is hanging on by a claw. In 50 years, I don’t suppose we’ll have polar bears right here.”

Within the meantime, polar bears gained’t change to a completely bird-based weight loss program, because it doesn’t present sufficient energy. An grownup polar bear needs about 54 Common Eider eggs to fulfill its every day power requirement. That day, the bear ate about 255 eggs—equal to a yearling ringed seal, and sufficient meals for lower than 5 days. 

And whereas some birds are threatened by polar bears, others partly depend on them for meals: When polar bears kill seals, quite a lot of birds feast on the leftovers, together with Ivory Gulls, Tough-legged Hawks, and Snowy Owls. “There’s a complete trophic cascade that comes from taking sea ice out of an ecosystem,” Derocher says. That system is fragile, and deeply interconnected.

Arctic sea ice decline is among the many most important climate-driven habitat losses on the planet, reshaping ecosystems and dangerously rewriting predator-prey dynamics. Confronted with these threats, “we will’t lose sight of the massive image,” Lyons says: Taking climate action at a global scale. Annually, sea ice loss is immediately proportional to human-caused fossil gas emissions. For bears and birds alike, the long run is unsure. The reason for that uncertainty, and its options, usually are not.