Antarctic penguins are breeding earlier at record speeds as local temperatures rise
Some colonies have advanced breeding by up to 24 days, scientists say
Researchers warn the shift could increase competition for food and nesting space
Warming in Antarctica driven by climate change is forcing penguins in the region to breed significantly earlier than before, with some species advancing their breeding season by up to 24 days, scientists have found.
A new study published in the Journal of Animal Ecology found that penguin colonies across parts of Antarctica are experiencing rapid local warming, prompting record-breaking shifts in breeding behaviour.
Data from camera-mounted temperature loggers showed that penguin colony locations are warming at around four times the continental average — at roughly 0.3 degrees Celsius (°C) per year, compared with 0.07°C across Antarctica as a whole. Antarctica is already the second fastest-warming region on Earth.
The researchers found that penguins are advancing the timing of their breeding settlement by between 10 and 13 days per decade on average, with some colonies showing shifts of as much as 24 days per decade.
The study says these changes represent some of the fastest phenological — or seasonal timing — shifts ever recorded in animals and are likely to increase competition for food and nesting space, as well as competition between species.
Scientists analysed breeding timings over a ten-year period, from 2012 to 2022, among three penguin species, Adélie, chinstrap and gentoo, across 37 colonies in the Antarctic Peninsula and nearby sub-Antarctic islands.
Settlement is defined as the first day penguins continuously occupy their nesting area. Colony sizes ranged from a few dozen birds to several hundred thousand.
Gentoo penguins showed the most rapid changes, with average settlement advancing by 13 days per decade. In some colonies, the shift was as large as 24 days per decade. The researchers said this variability is consistent with previous findings showing gentoo penguins have greater flexibility in incubation and hatching behaviour.
“These shifts were some of the fastest phenological changes ever observed in any animal,” The study said. “Relative to global review of animal phenological responses to climate change, our data indicate Gentoos have undergone the fastest phenological shift on record for all bird species while Adélies and Chinstraps are respectively fourth and fifth.”
For Adélie and chinstrap penguins, settlement dates were linked to both spring air temperatures and the number of freezing days. Warmer spring conditions generally led to earlier settlement, while a greater number of days above zero in October was associated with delayed settlement. The study also found that Adélie settlement advanced when winter sea-ice coverage declined, while chinstrap settlement was linked to increases in net primary productivity — a measure of biological activity at the base of the food chain.
Researchers noted that when winter sea-ice cover shrank to around a 20 kilometre radius around colonies — particularly in 2016 at the southernmost sites — Adélie penguins advanced their settlement dramatically in response to sea-ice loss.
For chinstrap penguins, increases in October net primary productivity around colonies, particularly since 2018, were associated with earlier settlement.
“Increased net primary productivity in the coastal Antarctic Peninsula over the last decade is thought to be driven by increased glacial melt,” the study said. “which favours phytoplankton blooms through water stratification and micronutrient enrichment.”
The researchers said chinstraps — which rely heavily on krill — may respond differently to these changes than gentoos, which feed more frequently on fish. Adélies can also consume fish, but often at the cost of increased foraging effort, reduced breeding success and lower juvenile recruitment.
Historically, the three species have avoided direct competition by occupying different ecological niches — separating breeding timing, foraging behaviour and life-history traits. However, the study warns that climate-driven shifts in sea ice and temperature could increase overlap between species, intensifying inter-species competition.
The authors said gentoo penguins, which show greater behavioural flexibility, are likely to be the “winners” under ongoing warming. Chinstrap penguins could be particularly vulnerable if krill stocks decline, while Adélie penguins may experience more subtle but long-term impacts.
Geographically, the researchers found that southern, more polar colonies tend to settle later than northern, more temperate ones. However, colonies in the Weddell Sea region have remained largely stable, as that area has not yet experienced the same level of warming or sea-ice loss seen along the western Antarctic Peninsula.