Zavodovski Island, a volcanic outpost in Antarctica once known for hosting the world’s largest penguin colony, has undergone a striking ecological reversal. A new study estimates that the island’s chinstrap penguin population fell by nearly 63% between 2011 and 2025, reducing the number of breeding pairs from about 542,000 to 201,000.
The findings, published in Current Biology, are based on 14 years of satellite observations combined with a detailed drone survey conducted during the 2023 incubation period. The researchers say the decline represents the largest shift in penguin populations recorded at a single Antarctic location.
A colony measured from above
Studying a vast and remote breeding colony is difficult from the ground. In 2023, researchers traveled to Zavodovski during incubation and used a drone to capture thousands of high-resolution images across the island. They combined those images with satellite imagery collected at roughly five-year intervals from 2011 through 2025.
That paired approach gave the team both close-up coverage of the colony and a longer record of change. The resulting estimates showed a severe decline among chinstrap penguins, a species that depends almost entirely on Antarctic krill for food.
Over the same period, the island’s subantarctic macaroni penguins moved in the opposite direction. Their numbers increased by more than 28% between 2011 and 2016, making them the island’s most abundant penguin species. The change means Zavodovski no longer holds its former distinction through its chinstrap population.
Why the species mix changed
The researchers identify regional ocean warming as the main driver of the chinstrap decline. Rising temperatures have reduced supplies of Antarctic krill, the small crustaceans that form the core of the birds’ diet. For a population with such a strong reliance on krill, a sustained reduction in food availability can place pressure on breeding colonies at a large scale.
The data do not describe a modest fluctuation. The estimated loss amounts to more than 250,000 chinstrap breeding pairs over the study period. It is a change large enough, the researchers say, to raise the possibility that chinstrap penguins may need to be reclassified globally from Least Concern to Endangered.
Macaroni penguins increased on the island even as chinstraps declined, underscoring that climate-related ecological change does not affect every species in the same way. The two populations occupy the same island but have not followed the same trajectory. In this case, the shift altered which penguin species is numerically dominant at Zavodovski.
A visible signal of ocean change
Antarctica is often perceived as distant from human activity, but the study presents the island’s changing colonies as evidence that warming conditions are reshaping even places inhabited only by animals. The authors characterize penguins as living indicators of environmental change because population trends can reflect changes in the marine food web that may otherwise be hard to see.
For chinstrap penguins, the link is especially direct: less krill means less food for a species that relies almost exclusively on it. The scale of the population drop on Zavodovski gives the broader concern a specific, measurable form.
The work also shows the value of combining satellite and drone imagery. Satellite observations can track remote landscapes over years, while drone images can provide the detailed coverage required to count colonies more precisely. Together, the methods enabled the researchers to compare the island over a 14-year period and quantify an ecosystem shift that would be difficult to observe through intermittent field visits alone.
What the result does—and does not—show
The study reports a major decline at one Antarctic location, not a complete global census of chinstrap penguins. Its warning about a possible conservation-status reassessment reflects the severity of the Zavodovski results and the need to understand whether comparable changes are occurring elsewhere.
Even so, Zavodovski is important because of the scale of its former colony. A fall from roughly 542,000 to 201,000 breeding pairs is not simply a change in a local count; it has changed the biological character of an island long identified with chinstrap penguins.
The researchers’ results provide a sharper baseline for continued monitoring. Future surveys can test whether the population stabilizes, continues to decline, or responds differently as ocean conditions change. They can also help establish whether the increase in macaroni penguins persists.
For now, the clearest conclusion is that a remote Antarctic colony has shifted dramatically within little more than a decade. The chinstrap population’s steep fall, alongside the rise of macaroni penguins, offers an unusually vivid measure of how warming seas and changing food supplies can reorganize an ecosystem.
This article is based on reporting by Phys.org. Read the original article.
Originally published on phys.org
