After 44 Years Of Observation, AK Guillemot Colony Collapsing As Ice & Cod Vanish
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.
The Cooper Island colony wouldn't be there at all if it weren't for Divoky. Cooper Island is flat, unlike the tall cliffs and rocky slopes where Mandt's black guillemots usually nest. But while surveying the Island for the Smithsonian Institution in 1972, Divoky found a few guillemots nesting beneath crates and pieces of wood left by the U.S. Navy in the 1950s. He turned over some more pieces of debris to make new nesting cavities, and guillemots immediately moved into them.
Recognizing the research opportunities that an accessible guillemot colony presented, Divoky returned a few years later to set out wooden nest boxes, eventually building up to around 200 boxes. Each year he would document the birds' family lives, traveling on his own dime when he couldn't get other funding. For the past seven years, he has also placed tracking devices on some of the birds so he could learn about their winter journeys to the Bering Sea ice.
EDIT
https://www.insidescience.org/news/seabirds-abandon-eggs-after-winter-without-ice
