One summer time 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 lot. By the top of the day, nearly all of them had 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 group had stumbled upon a rising menace to Arctic seabirds: hungry polar bears.
Because the Arctic warms, polar bears are shedding the summer time sea ice the place they hunt seals, their major prey. That’s driving them onto land, the place they more and more forage for seabird eggs, nestlings, and generally adults. Whereas the habits just isn’t new, researchers are observing it extra typically within the Canadian Arctic, Svalbard, and Greenland in latest a long time.
A new scientific paper, revealed in Polar Analysis this month, gives the primary report of large-scale bear-bird predation in Alaska, confirming that it’s occurring throughout the Arctic.
On these small islands, one or two polar bears can devastate a whole colony.
On Alaska’s north coast, the shore is generally low tundra fronted by barrier islands within the Beaufort Sea. These islands are important nesting grounds for seabirds, past the attain of conventional predators like Arctic foxes. Traditionally, polar bears hardly ever appeared right here in summer time, however as sea ice has melted, their numbers have elevated sixfold previously 20 years. Nests are significantly weak to predation on these small islands, the place one or two polar bears can devastate a whole colony.
The paper stories on two colonies: Cooper Island’s Black Guillemots and Spy Island’s Frequent Eiders.
Small and gravelly, Cooper Island is the long-time summer time dwelling of Mandt’s Black Guillemots, an Arctic subspecies. These birds initially nested beneath planks, ammo 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 way of 2010, bears killed practically half of all nestlings. In 2011, researchers put bear-proof nest instances on the island, however ultimately, bears discovered to interrupt them open, even submerging them in water to flush out grownup birds. In 2024 and 2025, bears precipitated 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, stories of bear predation had been uncommon since surveys started within the Nineteen 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 menace isn’t existential. Certainly, “most seabird species within the Arctic are nonetheless in comparatively fine condition,” says Don Lyons, director of conservation science at Audubon’s Seabird Institute. “They’re not liable to extinction within the subsequent 50 years. However the’’re going to face actual challenges, and will turn into endangered in that timeframe.”
For these two species as a complete, the polar bear menace isn’t existential.
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 menace to Pacific Frequent Eiders,” says Shively. For the guillemots, hotter waters imply fewer Arctic cod, their major meals.
In comparison with these threats, polar bears could also be solely a short-term downside, however for an unlucky cause, 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 assume we’ll have polar bears right here.”
“In 50 years, I don’t assume we’ll have polar bears right here.”
Within the meantime, polar bears gained’t swap to an entirely bird-based food plan, because it doesn’t present sufficient energy. An grownup polar bear needs about 54 Common Eider eggs to satisfy its each 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 straight proportional to human-caused fossil gasoline emissions. For bears and birds alike, the long run is unsure. The reason for that uncertainty, and its options, will not be.
