Thousands of birds perished in the Bering Sea. Arctic warming may be to blame

Thousands of puffins and other seabirds in the Bering Sea appear to have died in the winter of 2016 to 2017. The birds look like they starved to death, but the ultimate culprit was probably climate change, scientists say.

From October 2016 to January 2017, more than 350 dead birds, mostly tufted puffins, washed ashore at St. Paul Island, Alaska, on the Bering Sea. The birds were emaciated, and many had been molting when they perished. The period when birds regrow new coats of feathers is a particularly high-stress time for puffins and other birds because the animals need extra food while also being temporarily unable to fly.

The condition of the birds’ bodies points to starvation as the cause of death, scientists led by Timothy Jones, a biologist at the University of Washington in Seattle, report May 29 in PLOS ONE. Based on wind speed and direction across the Bering Sea that fall and winter, as well as the number of carcasses that washed ashore on St. Paul Island, but not on a neighboring island, the researchers estimate that between 3,150 and 8,800 birds died during that period.

The deaths are probably linked to elevated sea-surface temperatures in the eastern Bering Sea, a result of human-caused climate change, the team suggests. In the past, summertime sea ice melt has helped fuel blooms of plankton that form the base of the food web in the sea (SN: 3/16/19, p. 20). But sea ice has become scarce in the Bering Sea in the last few years, and there are fewer plankton blooms. That has had cascading effects through the sea’s food web, including decreases in some species of small fish, such as capelin and herring, that puffins eat.

Starvation may also have been responsible for recent mass die-offs of other seabirds in the region, such as of murres, auklets and kittiwakes.