Antarctic penguins are breeding earlier as the Peninsula rapidly warms, study finds

Penguins are running out of winter

The penguins on the Antarctic Peninsula are running out of winter.

A decade ago, Adélie, chinstrap and gentoo penguins typically began settling onto bare rock to build nests in late October or early November, just as spring loosened its grip on the ice. Now, researchers say, many of those same colonies are bustling nearly two weeks earlier, with birds jockeying for nest sites on ground that used to be buried in snow.

That shift in timing is not a fluke, scientists report. It is among the fastest changes in seasonal behavior documented in any bird—and potentially any vertebrate—and it is unfolding in one of the world’s fastest-warming regions.

A decade of cameras tracks a rapid shift

In a study published Jan. 19 in the Journal of Animal Ecology, an international team analyzed a decade of images from 77 time-lapse cameras monitoring 37 colonies around the Antarctic Peninsula. Between 2012 and 2022, the researchers found, the start of breeding advanced by roughly two weeks per decade on average, with gentoo penguins at some sites shifting by as much as 24 days earlier per decade.

“Penguins are changing the time at which they’re breeding at a record speed, faster than any other vertebrate,” said lead author Ignacio Juarez Martínez of the University of Oxford in an interview released with the study.

The work was coordinated by Oxford’s Penguin Watch project alongside the British Antarctic Survey and partners in the United States and Argentina. Researchers say it offers a rare, high-resolution look at how quickly wildlife can adjust its calendar as the climate changes—and hints at a growing divide between species that can keep up and those that may be pushed past their limits.

How the study measured penguin “settlement”

The team focused on three closely related “brush-tailed” penguin species—Adélie, chinstrap and gentoo—that share many breeding sites along the peninsula and surrounding islands but differ in their reliance on sea ice and their diets.

Using hourly images from rugged, solar-powered cameras positioned near colonies, the researchers identified the annual “settlement” date: the first day adults were continuously present on nesting areas. With those records—and with help from millions of image classifications submitted by citizen scientists through Penguin Watch—they inferred when eggs were laid, when they hatched and when chicks were being reared.

Each camera also recorded local air temperature, allowing the team to connect behavior directly to conditions at breeding sites.

Over the decade, those sites warmed by about 0.3°C (0.54°F) per year, totaling roughly 3°C—about four times the average rate of warming measured across Antarctica in recent decades.

“The idea of this whole monitoring network is to put something in place that does both population and behavioral monitoring,” said Tom Hart, a senior author on the paper and founder of Penguin Watch. “Ecologists are good at counting populations to show trends, but often the early warnings of decline can be found in the behavioral change of animals, which can be very hard to monitor. This study proves the benefits of monitoring animals at a landscape level.”

Gentoo shift fastest; specialists lag behind

The analysis found clear differences among species:

• Gentoo penguins, which are less dependent on sea ice and have a more flexible diet, advanced breeding the most—about 13 days earlier per decade on average across the study area, with some colonies shifting up to 24 days earlier per decade.
• Adélie and chinstrap penguins, more tightly tied to polar conditions and Antarctic krill, also moved earlier but more slowly—about 10 days per decade on average.

Across all species and sites, the breeding season now begins roughly two weeks earlier than it did 10 years ago.

Why timing matters in the Antarctic

In ecological terms, this kind of shift in “phenology”—the timing of recurring life events such as breeding or migration—matters because it helps animals match their behavior to seasonal conditions.

In the Antarctic, the window for raising chicks is short. Adults must lay eggs and feed fast-growing young when food is most available and weather is least severe. If warming brings earlier snowmelt and earlier access to the sea, penguins may benefit from nesting on clearer ground sooner.

But if prey does not shift on the same schedule, chicks could hatch before key food peaks—especially for krill—creating a trophic mismatch that has contributed to breeding failures in other seabirds.

“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,” Juarez Martínez said.

Scientists involved in the study said it remains unclear whether earlier breeding is helping or harming colonies.

“As penguins are considered ‘a bellwether of climate change,’ the results of this study have implications for species across the planet,” said co-author Fiona Jones of Oxford. “Further monitoring is needed to understand whether this record advance in the breeding seasons of these penguin species is impacting their breeding success.”

Winners, losers—and rising competition

The phenology shift is occurring alongside longer-term population changes on the Antarctic Peninsula.

• Adélie penguins, which depend on sea ice for foraging, have declined sharply in parts of the peninsula as ice has retreated and krill availability has shifted. Prior modeling suggests up to 60% of their current habitat could become unsuitable by century’s end under high-emissions scenarios.
• Chinstrap penguins, krill specialists that forage in open water, have also declined in much of the region. Some projections cited by researchers suggest the species faces a risk of regional—or even global—extinction by 2100 if current trends continue.
• Gentoo penguins, by contrast, have largely increased and expanded their range southward as conditions have grown more subpolar.

“Our results indicate that there will likely be ‘winners and losers of climate change’ for these penguin species,” Juarez Martínez said. “Specifically, the increasingly subpolar conditions of the Antarctic Peninsula likely favour generalists like gentoos at the expense of polar specialists like the krill-specialist chinstraps and the ice-specialist Adélies.”

As gentoo penguins shift their breeding earlier more quickly than their neighbors, the study notes, their nesting calendar now overlaps more with Adélies and chinstraps at many sites. That could intensify competition for limited ice-free nesting ground and for food in nearby waters during critical periods.

Fisheries pressures add another stressor

The changes at penguin colonies also intersect with human activity offshore. The Southern Ocean’s krill fishery—regulated by the Commission for the Conservation of Antarctic Marine Living Resources—has grown in commercial importance as krill is harvested for dietary supplements and aquaculture feed.

Scientists have warned that concentrated krill catches near predator breeding grounds, combined with warming and reduced sea ice, can stress penguin populations. In one recent season, the fishery hit its 620,000-ton catch limit in parts of the Antarctic Peninsula region earlier than expected, prompting an early closure and renewed concerns about local krill depletion.

While the new study did not assess fisheries directly, researchers said the findings add to evidence that penguins in the region are navigating rapid environmental change on multiple fronts.

A warming calendar, captured frame by frame

The camera network is expected to remain in place for years, and scientists hope continued monitoring will clarify whether earlier breeding is a successful adjustment—or a temporary shift that cannot keep pace with accelerating climate change.

For now, the photographs tell a stark story: in just 10 years, the rhythm of the Antarctic breeding season has changed. Nests fill earlier. Eggs are laid and hatch sooner. Chicks take their first steps under a higher, warmer sun.

“As the settling-in day comes earlier,” Juarez Martínez said, “all the other phenological milestones of their life cycle also come earlier: egg-laying, hatching, raising the chicks.”

For many readers, penguins are familiar symbols of a distant, frozen wilderness. For scientists, the new study suggests they are also precise, living timekeepers of a climate that is shifting faster than most species—or people—are used to seeing on the calendar.