Polar bears devastating Arctic seabird colonies as sea ice vanishes

Scientists have documented a worrying new pattern in the Arctic: polar bears, increasingly stranded on land by vanishing sea ice, are raiding seabird nesting grounds on a scale never before seen in Alaska.

A study led by the Wildlife Conservation Society (WCS) and Cooper Island Arctic Research, published in Polar Research, links the behaviour directly to the collapse of the bears’ traditional hunting grounds.

The research draws on decades of seabird monitoring data from Cooper Island – one of the longest unbroken records of its kind anywhere in the Arctic – to track how bear behaviour has shifted as sea ice retreats earlier and further each summer. With seals harder to reach, bears are spending far more time ashore, and many have turned to eggs and chicks as an alternative food source.

The most striking incident came in July 2024, when a lone bear spent almost a full day moving methodically through a common eider colony on Spy Island, destroying nearly nine in ten nests before it left. Researchers describe it as the largest single act of nest destruction by a polar bear ever recorded in the state.

Cooper Island itself tells a similar story. Bear incursions there increased markedly after sea ice hit record lows in 2007, and the animals have since worked out how to break into nest boxes that were specifically designed to keep them out. In 2024 and 2025, bear predation wiped out the island’s entire black guillemot breeding season.

“For decades these barrier islands served as places where seabirds could nest with relatively little pressure from large land predators,” said Kayla Shively, Conservation Ecologist with WCS’s Arctic Beringia Programme and lead author of the study. “What we’re seeing now is that as polar bears spend more time on shore, those relationships are changing. It’s another reminder that climate change isn’t affecting one species at a time – it is reshaping the connections between species across the Arctic.”