Extreme snowstorms decimate Antarctic petrel nests

A spate of intense storms in 2021 has been blamed for the breeding failure of two Antarctic seabird colonies.

For decades, two of the largest Antarctic petrel colonies in the world, called Svarthamaren and Jutulsessen, contained hundreds of thousands of nests. In the 2021/2022 breeding season, however, there were almost zero.

'We know seabird colonies lose some chicks and eggs when there's a storm, and breeding success will be lower,' says Dr Sebastien Descamps, the lead author of a paper recording the decline. 'But here we're talking about tens - if not hundreds - of thousands of birds, and none of them reproduced throughout these storms.'

The storms have had far reaching consequences in Antarctica. Fewer seabirds were spotted at sites more than 600 kilometres away, with some colonies said to be 'deserted'.

'Not only were so many birds hit by the storms, but this extreme weather also affected colonies spread over hundreds of kilometres,' Sebastien adds. 'The breeding success of a large part of the Antarctic petrel population was impacted.'

The extreme weather is thought to have been a result of climate change, which has been predicted to make storms more intense in the coming years.

While there is no immediate danger to the survival of the Antarctic petrel, the study published in Current Biology suggests that it could put additional pressure on seabird colonies that are already at risk of collapse.

How does climate change cause snowstorms?

While climate change is generally associated with high temperatures, it can also affect cold weather. Warmer air is capable of holding more moisture, which can lead to storms becoming more severe.

On average, air can hold around 7% more water each time its temperature increases by 1°C. As the world heats up, this means that warmer regions are likely to see more intense rainstorms, while colder regions will see more snow.

Alongside other impacts of climate change, such as the rising temperature of the oceans, this leads to more moisture entering the atmosphere. In Antarctica, this means more extreme snowstorms, which is problematic for the petrels.

The birds normally nest on rocky ledges and slopes, relying on them for snow-free areas to lay their eggs, but the extreme storms have increased the amount of snowfall at both colonies.

As a consequence, more than half the normal breeding area at Svarthamaren was inundated by snow in 2022, leaving just three occupied nests. As the birds also need to use more energy keeping warm and finding shelter during storms, this may have made egg-laying too risky for them.

Aside from the Antarctic petrels, the storms have also had knock on effects for other seabirds. Only a few snow petrel nests were observed at both sites, while no polar skua nests were seen whatsoever.

As all three species breed widely across Antarctica, there is no imminent risk that they will become extinct. Dr Alex Bond, Principal Curator and Curator in Charge of Birds at the Museum, says that seabirds are capable of bouncing back from years where breeding is low.

'Seabirds are long-lived species with high adult survival, so each pair only needs to successfully reproduce a couple of times in their lifetime to ensure their replacement in the populations,' Alex says.

'This means they will almost always prioritise their own survival over breeding, so missing a year of breeding isn't a huge deal. It's a sensible strategy when things are tough as it means the pair can try again next year without having spent the energy, or taken the risk, of breeding.'

While the seabirds are safe for now, there has been a general decline in the number of Antarctic petrel breeding pairs at Svarthamaren since the 1980s, which the paper found that storms mostly accounted for.

If extreme Antarctic storms become more common, then it could make it a struggle for seabirds on Earth's southernmost continent to survive.