With their nesting sites buried under a blanket of snow, some petrels and skuas made no attempts at reproducing in December 2021 and January 2022

Snow petrels were among the seabird species that did not reproduce in Antarctica’s Dronning Maud Land region in 2021-22. Natalie Tapson via Flickr under CC BY-NC-SA 2.0

Every November and December, hundreds of thousands of polar seabirds lay their eggs on bare ground on Antarctica as the Southern Hemisphere summer begins. They dutifully protect the eggs until they hatch, then switch into new-parent mode and care for the chicks. By February or March, those hatchlings are typically strong enough to fly.

That’s the normal timeline of events for birds like the Antarctic petrel, the snow petrel and the south polar skua. But in one large region of the White Continent during the 2021-22 breeding season, none of it actually happened, according to a new paper published last week in the journal Current Biology.

In December 2021 and January 2022, violent snowstorms swept over Dronning Maud Land, a massive, Norwegian-claimed area that makes up one-sixth of Antarctica. So much snow accumulated that the birds could not find the bare ground they needed to lay their eggs.

As a result, the three species did not breed last year on part of the continent. Instead of the tens of thousands of active nests usually seen at the mountainous breeding sites of Svarthamaren and Jutulsessen, researchers found hardly anything—just three nests of Antarctic petrels, a handful of nests from snow petrels and zero nests of south polar skuas.

Antarctic petrels, as well as other seabirds, spend most of their lives flying over the open ocean. François Guerraz via Wikimedia Commons under CC BY-SA 3.0

Because they didn’t find any dead chicks—only empty nests—the scientists suspect the birds didn’t even attempt to breed because of the tough conditions and simply returned to sea. These three species, as well as other seabirds, spend the majority of their lives soaring over open waters, where they feast on fish and krill. The only moments they spend on land are for once-a-year breeding and chick-raising.

“They’re very adapted,” says study co-author Harald Steen, an ecologist at the Norwegian Polar Institute, to Gizmodo’s Angely Mercado. “They can cope, but if the frequency of these breeding failures increases, then we will expect that the colonies will diminish in the long run.”

Though storms can result in the loss of some eggs and chicks, it’s very unusual for entire seabird colonies to skip reproducing entirely. Last year’s breeding failure is “really unexpected,” says study co-author Sébastien Descamps, a researcher at the Norwegian Polar Institute, in a statement.

Human-caused climate change is likely to blame for the unusually strong snowstorms last year, the researchers suggest. Climate change models predict that rising temperatures in Antarctica will likely contribute to increased snowfall on the continent. And already, extreme wind events are becoming more frequent and severe. If these trends continue, they may hasten the decline and, possibly, the local extinction of some Antarctic seabirds, the researchers write in the paper.

As for the south polar skuas, they prey on the eggs and chicks of Antarctic petrels, so the absence of these other seabirds likely contributed to their lack of reproduction, per the paper.

Still, the loss of one breeding season may not necessarily make much of an impact on overall populations of Antarctic petrels, snow petrels and south polar skuas. These birds can live for a long time—between 15 and 25 years—and, as a result, have “many chances to breed successfully throughout their lifespan,” says Heather J. Lynch, a conservation biologist and statistician at Stony Brook University who was not involved in the study, to New Scientist’s Jason Arunn Murugesu.

“It’s possible that the long-term impacts of this particular event, though startling to witness, may be muted,” she adds to New Scientist. “It will take many years and further monitoring to know for sure.”

source: https://www.smithsonianmag.com/