The short version
- Chinstrap penguin nests on Zavodovski Island dropped by 63 percent between 2011 and 2025, ending its status as the world's largest colony.
- Researchers attribute the decline to climate-driven ocean warming that pushes krill southward, beyond the reach of cold-adapted chinstraps.
- Macaroni penguins on the same island have increased in number due to their ability to forage in warmer waters and consume a more varied diet.
The remote volcanic island of Zavodovski, once recognized as home to the largest penguin colony on Earth, has experienced a dramatic shift in its avian population. Recent aerial surveys conducted by the British Antarctic Survey indicate that the number of occupied chinstrap penguin nests fell by approximately 63 percent between 2011 and 2025. This steep decline marks a significant ecological change in the South Sandwich Islands, a UK overseas territory located north of the Antarctic continent.
The loss of this population means Zavodovski no longer holds the title for the world’s largest penguin colony. That distinction has reportedly shifted to Cape Adare in the Ross Sea, situated more than 5,000 kilometers away on the opposite side of the continent. The research team described the drop in chinstrap numbers as alarming, suggesting that the species may now be officially classified as endangered due to these rapid environmental pressures.
Scientists point to climate change as the primary driver behind this collapse. Rising ocean temperatures are altering the distribution of krill, the staple food source for chinstrap penguins. As waters warm, krill populations have moved further south toward sea ice. Chinstrap penguins, which prefer cooler waters and rely on a specialist diet, cannot easily follow their prey because suitable nesting islands do not exist in those southern regions.
The study utilized drones, aerial photography, and tracking devices fitted to twenty birds to monitor the colony’s health. The British Antarctic Survey noted that conducting fieldwork in this location is among the most extreme challenges in polar research, requiring a fifteen-day voyage to reach the site. Despite the logistical difficulties, the data collected provides a clear picture of how warming impacts sensitive ecosystems in the Antarctic.
While chinstrap numbers have plummeted, the island’s macaroni penguin population has surged. This divergence highlights differing adaptive strategies between the two species. Macaroni penguins possess a more flexible diet and are capable of foraging in warmer waters to the northeast of the island. There, they supplement their intake with fish and other crustaceans, allowing them to thrive even as conditions become less favorable for their cold-adapted neighbors.
Researchers considered other potential threats to the chinstrap population, including volcanic activity and competition from migrating humpback whales. Mount Curry, an active volcano on the island, emits fumes that have given nearby sites names like Stench Point and Asphyxia Plain. However, the steady decline observed since 2011 predates any recent major volcanic eruptions, with the last significant event occurring in 2016. Additionally, while humpback whales consume large quantities of krill, their waste fertilizes marine plants that support krill production, making them unlikely to be the primary cause of the shortage.
The findings suggest a fundamental shift in the community composition of this Antarctic region. Professor Norman Ratcliffe, who led the research, described the changes as the biggest ever observed at a single location in Antarctica. The data indicates that cold-adapted species are struggling to coexist with sub-Antarctic neighbors as rapid warming reshapes the local environment.
These results underscore the vulnerability of specialized species to climate-induced changes in food availability. As ocean temperatures continue to rise, the geographic mismatch between predators and their prey is likely to intensify. The study, published in Current Biology, serves as a stark indicator of how quickly unique ecosystems can transform under environmental stress.
The implications extend beyond Zavodovski Island, offering broader insights into Antarctic biodiversity trends. The contrast between the declining chinstrap population and the thriving macaroni colony illustrates that not all species will respond uniformly to warming waters. Understanding these dynamics is crucial for predicting future shifts in marine ecosystems and informing conservation efforts in polar regions.
Sources behind this briefing
Go to the original reporting
- BBC Science & Environment↗World's largest penguin colony hit by 'alarming' decline in numbers
