SOURCE: Inside Science

DATE: December 28, 2019

SNIP: Each winter, sleek seabirds known as Mandt’s black guillemots descend on the ice that forms over the Bering Sea between Alaska and Russia. They spend the season diving under the ice to catch Arctic cod and resting on the frozen surface. But last winter, ice in the Bering sea was at record lows, forming later and melting far sooner than usual.

According to ornithologist George Divoky, this loss of winter sea ice could be “the final nail in the coffin” for a colony of birds already struggling with other aspects of climate change.

The breeding colony in question is located on Cooper Island off the north coast of Alaska, and Divoky has been studying it for 44 years. Twenty-eight percent of the birds that left in the fall of 2017 never returned to the island — the highest apparent overwinter mortality ever documented for the colony, up from around 10 percent in a typical year. And while hundreds of guillemots raised chicks on the island in past decades, only 50 pairs laid eggs this year. Half of those clutches were never incubated.

“I would see a pair on the nest site, and I would go, ‘wait a minute, you guys have eggs.’ And I’d open the [nest box], and the eggs would be cold,” said Divoky. He described it as a “mass egg abandonment” — something he had never seen before. He presented the findings earlier this month at the American Geophysical Union meeting in Washington.