A Snow Petrel stands on the frozen Southern Ocean. Photo by Tarpan/Shutterstock

The arrival of the new year is a prime time for Antarctic birds like the South Polar Skua, Antarctic Petrel, and Snow Petrel to build nests and lay their eggs. However, from December 2021 to January 2022, researchers did not find a single skua nest on Svarthamaren, one of the regions where the birds go to raise their young. Similarly, the number of Antarctic and Snow Petrel nests dropped to almost zero.

In these regions, climate change caused snowfall and snow accumulation to be significantly higher than in previous years. Now, a study published on March 13 in the journal Current Biology shows that these unusually strong snowstorms have interfered with the birds’ ability to breed.

“We know that in a seabird colony, when there’s a storm, you will lose some chicks and eggs, and breeding success will be lower,” says Sebastien Descamps, first author of the study and researcher at the Norwegian Polar Institute. “But here we’re talking about tens if not hundreds of thousands of birds, and none of them reproduced throughout these storms. Having zero breeding success is really unexpected.”

An Antarctic Petrel paddles on the water between ice floes. Photo by Tarpan/Shutterstock

Svarthamaren and nearby Jutulsessen are home to two of the world’s largest Antarctic Petrel colonies and are essential nesting grounds for Snow Petrels and South Polar Skuas. From 1985 to 2020 in Svarthamaren, the colony contained between 20,000 and 200,000 Antarctic Petrel nests, around 2,000 Snow Petrel nests, and over 100 skua nests annually.

In the 2021–2022 season, there were only three breeding pairs of Antarctic Petrels, a handful of breeding Snow Petrels, and zero skua nests. Similarly, in Jutulsessen, there were no Antarctic Petrel nests in summer of 2021 to 2022 despite previous years having shown tens of thousands of active nests.

“It wasn’t only a single isolated colony that was impacted by this extreme weather. We’re talking about colonies spread over hundreds of kilometers,” says Descamps. “So, these stormy conditions impacted a really large part of land, meaning that the breeding success of a large part of the Antarctic Petrel population was impacted.”

Second-year South Polar Skua in the Atlantic Ocean. Photo by Agami Photo Agency/ Shutterstock

These birds lay their eggs on bare ground, so with enough snow, the ground becomes inaccessible, and chick-raising becomes impossible. The storms also have a thermoregulatory cost — the birds must spend their available strength sheltering, keeping warm, and conserving energy.

“Until recently, there were no obvious signs of climate warming in Antarctica except for on the peninsula,” says Descamps. “But in the last few years, there have been new studies and new extreme weather events that started to turn the way we see climate change in Antarctica.”

Descamps hopes that over time, the model used to predict storm severity can be adjusted to be even more accurate. “When it comes to storm severity, it’s both the wind and the snow accumulation,” he says. “There aren’t many places where we have the right kinds of snow measurements, and it plays an important role in explaining the breeding success of the birds.”

“I think our study shows in a very strong way that these extreme events do have a very strong impact on seabird populations, and climate models predict that the severity of these extreme events will increase,” says Descamps.

source: https://www.birdwatchingdaily.com