World's Largest Penguin Colony Faces Alarming Decline

Zavodovski Island, once home to the world's largest colony of chinstrap penguins, has experienced an 'alarming' decline in numbers, according to new aerial surveys. Researchers report that between 2011 and 2025, the population of occupied chinstrap penguin nests decreased by 63%. Scientists attribute this drastic reduction to climate change, which is affecting the birds' food supply and survival.

A Shifting Ecosystem

The chinstrap penguins' specialized diet, primarily krill, and their preference for cooler waters appear to have left them vulnerable as ocean temperatures rise. The krill have moved southwards, but warming seas and a lack of suitable nesting islands prevent the chinstrap penguins from following their food source. This has led to a significant drop in their population.

In contrast, macaroni penguins, also nesting on Zavodovski Island, have seen their numbers increase. Scientists believe this is linked to the macaroni penguins' more varied diet and their ability to forage in warmer waters to the northeast of the island, supplementing their diet with fish and crustaceans.

This shift represents "the biggest change in community composition ever observed at a single location in Antarctica," said Professor Norman Ratcliffe, who led the research. "Our data shows that the cold-adapted Antarctic chinstrap species are no longer thriving beside their sub-Antarctic neighbours," he added. "It is further evidence of how rapid warming in the Antarctic is impacting unique and sensitive ecosystems."

Zavodovski Island

Zavodovski Island is part of the South Sandwich Islands, a remote archipelago north of the Antarctic continent and a UK overseas territory. In 2011, the British Antarctic Survey (BAS) identified it as hosting the largest penguin colony globally, with an estimated 600,000 chinstrap penguins and 90,000 macaroni penguins. The island is characterized by its bleak, rocky terrain and the active volcano Mount Curry.

The research team, led by BAS, undertook extensive fieldwork, including sailing for 15 days to reach the island. They utilized drones, aerial photography, and tracking devices fitted to 20 birds to gather data. While an eruption of Mount Curry in 2016 occurred, the study indicates the penguin decline has been a steady, ongoing trend since 2011, suggesting climate-driven factors are the primary cause.

The title of the world's largest penguin colony now belongs to Cape Adare in the Ross Sea, over 5,000 km away. The findings of this research have been published in the journal Current Biology.