Warming shifts penguin breeding earlier on Antarctic Peninsula, study finds

Penguins on the Antarctic Peninsula have started breeding earlier than ever recorded, a shift scientists link to rapid warming in one of the planet’s fastest-changing regions.

A decade of time-lapse images from 37 colonies shows 3 species — Adélie, chinstrap and gentoo penguins — advanced the start of breeding at “record rates” between 2012 and 2022, according to a study published online Jan. 19 in the Journal of Animal Ecology. Gentoo penguins showed the biggest change, advancing an average 13 days per decade, with some colonies moving up as much as 24 days, the study found. Adélie and chinstrap penguins advanced about 10 days on average. Researchers called the gentoo shift the fastest phenology change recorded for any bird and possibly any vertebrate.

The timing matters because penguins build their breeding schedules around environmental cues such as air temperature, sea ice and food availability. Shifting those cues can push penguins to lay eggs earlier, hatch chicks earlier and hunt earlier — but the food chain may not move in lockstep.

“The time at which you breed needs to coincide with the time with most resources in the environment and this is mostly food for your chicks so they have enough to grow,” said Ignacio Juarez Martinez, a biologist at the University of Oxford and the study’s lead author.

Researchers cannot yet say whether earlier breeding helps or harms the penguins overall. But the study and outside experts warn it could widen gaps between species that already face different pressures from warming, changing sea ice and shifting prey.

“This shift in breeding timing is an interesting signal of change and now it’s important to continue observing these penguin populations to see if these changes have negative impacts on their populations,” said Michelle LaRue, a professor of Antarctic marine science at the University of Canterbury in New Zealand, who was not involved in the research.

The work relied on a monitoring network designed for a region where scientists cannot easily remain year-round. Tom Hart, an ecologist at Oxford Brookes University and founder of Penguin Watch, said long-term Antarctic field research runs into harsh weather, remoteness and short field seasons.

“What could you do if you were present all year round?” Hart asked in an NPR interview. “If you could be omnipotent for a moment and you could actually watch in such a hostile, remote environment, what would you want to see?”

Hart and colleagues tried to approximate that constant presence using 77 time-lapse cameras placed across the Antarctic Peninsula and some sub-Antarctic islands. Each camera took photos every hour, building a decade-long record of colony “settlement,” defined as the first date penguins continuously occupied a nesting zone. Those cameras also carried thermometers. The team reported that temperatures at colony sites warmed about 0.3°C per year, roughly 4 times faster than the Antarctic continental average of 0.07°C per year cited in the study materials.

The broader region has warmed sharply over recent decades, though the rate varies by location and period. A Nature paper analyzing Antarctic Peninsula station records reported an annual mean warming trend of 0.46°C per decade at Faraday-Vernadsky station from 1951 to 2018 and 0.29°C per decade at Esperanza station from 1957 to 2016.

The study focused on 3 “brush-tailed” penguins that share parts of the peninsula but differ in diet and behavior. Adélie penguins tend to rely on sea ice and have a more polar niche. Chinstrap penguins often specialize on krill. Gentoo penguins eat a wider mix of prey and often behave as generalists.

That difference could shape who benefits from a longer, warmer season.

“Our results indicate that there will likely be ‘winners and losers of climate change’ for these penguin species,” Juarez Martinez said in a University of Oxford statement, arguing the peninsula’s “increasingly subpolar conditions” likely favor generalists such as gentoos over polar specialists such as chinstraps and Adélies.

The study’s abstract reaches a similar conclusion, describing gentoos as better suited to compete for space and resources than krill-specialist chinstraps and ice-specialist Adélies as breeding times converge. Fiona Suttle, a University of Oxford biologist and a co-author, told The Associated Press that the shift has started to erase a timing separation that once reduced competition among the species. In visits to colony areas in October and November, she said she has returned expecting to see Adélies and instead found gentoo nests.

The earlier schedule could also create a mismatch between chick hatching and peak food availability. In an AP interview, Juarez Martinez said the warming Antarctic Peninsula likely means less sea ice and earlier seasonal blooms at the base of the food chain. If krill timing shifts differently than penguin breeding, chicks could face food shortages during critical growth periods. The pace of change stood out even to researchers used to seeing climate-driven shifts. Suttle told the AP that scientists have documented a similar 2-week shift in breeding timing for great tits, a European songbird, but that change took about 75 years, not 10.

Hart said the penguin camera network also reflects a broader lesson about wildlife monitoring: behavior can reveal stress before population counts do. “Ecologists are good at counting populations to show trends, but often the early warnings of decline can be found in the behavioural change of animals,” he said in the Oxford statement.

Researchers cautioned that they do not know how much further penguins can shift if warming continues. The Oxford release noted statistical models point to temperature as a dominant driver of the breeding shift, but it remains unclear whether earlier breeding represents a successful adaptation or a risky mismatch with other ecological factors such as prey availability.

The team also relied on help from the public to process the huge photo archive. Suttle told the AP that volunteers tagged millions of images through the Penguin Watch platform, helping researchers identify breeding activity across colonies.