- Penguins on the Antarctic peninsula and surrounding islands are breeding substantially earlier in the year than just a decade ago, according to new research.
- The study used remote cameras to track the breeding season of three penguin species across 37 colonies from 2012 to 2022.
- Gentoo penguins advanced their breeding season by about 13 days over the 10-year period, while Adélie and chinstrap penguins each shifted breeding by about 10 days.
- Researchers don’t yet know how the changes are impacting penguins, but it could lead to a mismatch in food availability for chicks or create competition among species for food and other resources.
Penguins are dramatically shifting their breeding season as the Antarctic peninsula warms, a recent study finds.
From 2012 to 2022, researchers used remote cameras to examine the timing of breeding for three penguin species across 37 colonies on the Antarctic peninsula and surrounding islands. They tracked their ‘settlement date’: when the penguins began continuously occupying their nesting zones. The study, led by the citizen-science collective Penguin Watch at the University of Oxford and Oxford Brookes University, U.K., was published in the Journal of Animal Ecology.
Over that 10-year period, gentoo penguins (Pygoscelis papua) began their breeding season an average of 13 days earlier in the year, though for some colonies, it was more than three weeks. Chinstrap (P. antarcticus) and Adélie (P. adeliae) penguins settled into their colonies an average of 10.4 and 10.2 days, respectively, ahead of their schedule a decade ago.
These breeding changes are amongst the most extreme yet recorded for any bird — and likely any vertebrate — in response to climate change, the study notes.
“This is a huge advance and an incredibly fast one … and that’s what surprised us,” says Ignacio Juarez Martínez, a biologist and the study’s lead author who conducted the research as part of his PhD at the University of Oxford. “It’s literally a world record.”
A changing pole, earlier spring
Gentoo, chinstrap and Adélie penguins all nest in the austral spring — the southern hemisphere’s spring generally beginning in September — congregating on snow-free ground in colonies ranging from a dozen to hundreds of thousands of breeding pairs. Their breeding season is carefully timed to make the best of the extreme polar environment where they evolved. But as climate change accelerates, these penguins — and many other species — may find the timing of key events like breeding knocked out of whack.
“Moving that date, even though it can still be adaptive for one thing, can be catastrophic for other reasons,” Martínez says.
The breadth of the study — and deployment of camera traps far from established research stations — demonstrates that climate change is already having a “big effect” on penguin behavior across a large area, writes Michael Polito, an associate professor at the University of California Santa Cruz, U.S., who was not involved in the study, in an email.
The data indicate that the changes in the timing of penguin breeding are related to warming temperatures and changes in sea ice. The researchers don’t yet know exactly how the shift has impacted the penguins so far. To figure that out, Martínez is now analyzing data the team collected on chick survival.
An advancing breeding season
The pace of change is concerning. “One of the risks is what we call the phenological mismatch, which is that the penguins are advancing their season at a different rate than their prey. If either of them is advancing faster than the other, the penguins are going to suffer because they are not going to be able to have as much food, especially during the key time of chick rearing,” Martínez says.
Another concern is that these shifts in penguins’ breeding schedule will lead to more overlap and competition for resources, especially as the three species are responding to climatic changes at different rates.
Gentoo penguins showed the most variation in the timing of breeding, indicating that they might be more resilient, able to better respond to environmental changes. Though all three species are listed as ‘Least Concern’ on the IUCN Red List, Adélie and chinstrap penguins are declining across much of the Antarctic peninsula, while gentoos are increasing and expanding their range southwards. Increased competition could exacerbate these trajectories, Martínez says.
With just 1% of Antarctica ice-free in the summer months — only a portion of that found along the coast — nest space is at a premium.
Adélie and chinstrap penguins winter hundreds or thousands of kilometers away from their breeding grounds, along marginal ice zones or in the open ocean, north of the ice edge. Adélie penguins generally return and begin breeding first, followed by chinstraps. Gentoo penguins winter closer to breeding grounds and, though they sometimes occupy nests early in the season, they are the last to settle down to breed in earnest.
For now, Adélies and chinstraps can kick those early gentoos out: An angry bellow, followed by flipper slaps or beak jabs, usually does the trick, Martínez says. Partly, their success is “a matter of character … chinstraps and Adélies are much feistier.”
As the gentoo’s breeding season continues to advance, Martínez says he worries they could become more reluctant to leave. That would mean fewer nesting spots for the other species.
Another, perhaps more insidious threat, is that the overlap will increase competition for food.
Gentoo penguins eat both fish and krill, while the more specialist Adélie and chinstrap penguins depend heavily or exclusively on krill. Experts worry that with more competition for food, gentoos, as generalists, could gain the upper hand, especially in low-krill years.
The underlying problem is climate change, and the only real solution is to reduce emissions, says study co-author Fiona Jones, a biologist and science communicator at the University of Oxford. Penguins play a vital role in their ecosystems, cycling nutrients between the ocean and land, and even playing a role in cloud formation: Their droppings exude ammonia gas, which helps form clouds over the Antarctic, cooling the region, thus helping cool a place heavily impacted by global warming.
“… They are hugely important to the Southern Ocean ecosystem,” Jones says.
In the interim, we can lessen other pressures on penguins, Martínez says, including from an industrial-scale krill fishery.
Catch limits for krill in the Southern Ocean are set by an intergovernmental body, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Norway takes the largest share by far: Of the nearly 425,000 tonnes of krill trawled in 2023, Norway took 67%, followed by China (17%) and South Korea (8%), with Chile and Ukraine taking the rest.
Fishing is concentrated in areas favored by penguins — especially chinstraps — as well as other krill predators, leading to a disproportionate impact, says study co-author Tom Hart, Penguin Watch founder and senior lecturer at Oxford Brookes University.
Catches have increased over time, even as humpback whales (Megaptera novaeangliae) and other Southern Ocean baleen whales that thrive on krill in the region are making a comeback.
“This isn’t static. You can’t say ‘there’s enough krill to go around, we don’t think we’re having an impact’ when, at the same time, there are more mouths for krill,” Hart says.
In an unprecedented move in 2025, the krill fishery was shut down in August, reaching the 620,000-metric-ton limit months ahead of the normal December closure.
Penguins are a superb indicator species, says Hart: long-lived, relatively easy to monitor, and sensitive to changes both at sea and on land. The shifts in the timing of penguin breeding, described in the recent study, are an indication that change is afoot, and should not be ignored.
“I like the fact that we’re starting to look at behaviors that are important as early warning and not just looking at when whole populations start to crash, which should give us more time to act,” Hart says.
Banner image: Study co-author Tom Hart changes the batteries on a remote camera. Penguin Watch’s camera network includes more than 77 cameras that monitor penguin colonies year-round, providing a wealth of data. Image by Katherine Booth Jones.
Citations:
Belyaev, O., Sparaventi, E., Navarro, G., Rodríguez-Romero, A., & Tovar-Sánchez, A. (2023). The contribution of penguin guano to the Southern Ocean iron pool. Nature Communications, 14(1), 1781. doi:10.1038/s41467-023-37132-5
Boyer, M., Quéléver, L., Brasseur, Z., McManus, B., Herndon, S., Agnese, M., … Sipilä, M. (2025). Penguin guano is an important source of climate-relevant aerosol particles in Antarctica. Communications Earth & Environment, 6(1), 368. doi:10.1038/s43247-025-02312-2
Herman, R., Borowicz, A., Lynch, M., Trathan, P., Hart, T., & Lynch, H. (2020). Update on the global abundance and distribution of breeding Gentoo Penguins (Pygoscelis papua). Polar Biology, 43(12), 1947-1956. doi:10.1007/s00300-020-02759-3
Juarez Martínez, I., Kacelnik, A., Jones, F. M., Hinke, J. T., Dunn, M. J., Raya Rey, A., … & Hart, T. (2026). Record phenological responses to climate change in three sympatric penguin species. Journal of Animal Ecology. doi:10.1111/1365-2656.70201
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