First recorded failure of emperor penguin breeding in a single region, 2023 likely worse

The first case of multiple emperor penguin breeding colonies undergoing total breeding failure has been recorded and the outlook is just as bad for the upcoming summer.

Last year’s reduction in sea ice around west Antarctica is believed to be responsible for the breeding failure in four out of five surveyed emperor penguin (Aptenodytes forsteri) colonies, according to the British Antarctic Survey.

Emperor penguins (aptenodytes forsteri) on the sea ice close to halley research station.
Emperor penguins (Aptenodytes forsteri) on the sea ice close to Halley Research Station. Credit: Christopher Walton

Colonies lining the coast of the Bellingshausen Sea were largely abandoned by the start of the fledgling period in December due to sea ice loss, which reached record lows in 2020.

Imagery from Europe’s Sentinel2 satellites showed Pfrogner Point, Bryant Coast, Smyley Island and Verdi Peninsula had no signs of a present colony, but one at Rothschild Island managed to persist, potentially due to the unique geometry and iceberg presence in the island’s nearby bay. It’s likely chicks in the other four locations did not survive.

The emperor penguin is the largest of the world’s 18 penguin species. About 256,500 breeding pairs were estimated to live in Antarctica as of 2019. They are considered to be ‘near threatened’ by the IUCN.

Breeding in winter, they rely on stable sea and ‘land-fast ice’ which forms in winter months to establish successful crèches for their chicks, which can swim once they develop waterproof feathers as fledglings.

Overall, the Bellingshausen Sea – which borders the Antarctic coast closest to Chile and Argentina – saw the loss of at least half of previous sea ice compared to the 30-year average from 1991-2020, and complete loss in certain regions. The survey was undertaken in 2022 during was the worst year for sea ice formation in Antarctica since the beginning of records in 1979.

The record won’t stand long, with 2023 sea ice already 147 million hectares behind last year’s mark. That’s an area larger than the Northern Territory.

2022 (dotted red) and 2023 (light blue) sea ice extent in antarctica.
2022 (dotted red) and 2023 (light blue) sea ice extent in Antarctica is at record lows. Source: National Snow and Ice Data Center, Boulder Colorado

Expect worse for emperor penguins in 2023

“We already know that sea ice formed late this year at many colony sites,” the study’s lead researcher Dr Peter Fretwell tells Cosmos.

“In the Bellingshausen Sea the sea ice did not start to form until late June, when the birds should have already laid their eggs, so it is highly likely that this year will be just as bad if not worse [than 2022].”

While colony failures have been previously recorded since satellites started being used for observations 15 years ago, simultaneous multi-site abandonments had not been sighted until 2022, and only one study location had experienced a total breeding failure before.

Although Fretwell and his colleagues know adult emperor penguins are adaptable and can relocate to safer locations for breeding in subsequent years – sometimes by tens of kilometres – rapid loss of sea ice due to warming temperatures could test their resilience. In their research, they note “such a strategy will not be possible if breeding habitat becomes unsuitable at a regional scale”.

The British Antarctic Survey will continue monitoring the Bellingshausen Sea colonies into the Antarctic spring and summer.

“We are awaiting the rise of the sun, so that we can start to see how the colonies are fairing,” Fretwell says.

“We will continue monitoring and try to develop new techniques to increase our knowledge of the consequences and trajectories of emperor penguins.”

Antarctica’s four lowest annual sea ice extents have been recorded since 2016.

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