This island was home to the planet’s largest penguin colony. Here’s why it just lost that title
The decline can be linked to human-driven climate change, the report concludes.
A penguin colony on Zavodovski Island. (Photo Credit: John Dickens via CNN Newsource)
(CNN) — An uninhabited volcanic island in the Southern Ocean used to be home to the largest penguin colony in the world — but not anymore. Scientists have discovered the staggering loss of more than half a million chinstrap penguins from the isolated outcrop.
Chinstrap penguins, named for the narrow band of black feathers under their chins, thrive in harsh locations and Zavodovski Island fits the bill perfectly. Part of the South Sandwich Islands archipelago north of Antarctica, the island is wild, craggy and windswept.
Chinstrap penguin feeding chick on Signy Island in the South Orkney Islands, Antarctica. (Photo Credit: Richard Phillips via CNN Newsource)
Zavodovski is home to both chinstraps and macaroni penguins, which have distinctive yellow feather plumes on their heads. In 2011, it was named the largest penguin colony in the world, but when British Antarctic Survey researchers traveled to the island in 2023, they found the chinstraps had suffered huge declines.
More than half a million have been lost since 2011, representing a quarter of the island’s penguins, according to the the findings published Wednesday in the journal Current Biology. Comparing aerial surveys with satellite data, the researchers found the number of occupied chinstrap penguin nests fell by 63% between 2011 and 2025.
“It is the biggest change in community composition ever observed at a single location in Antarctica,” said Norman Ratcliffe, a penguin ecologist at BAS and the lead researcher. The decline can be linked to human-driven climate change, the report concludes.
“Chinstraps are giving quite a clear signal of the impacts of warming,” Ratcliffe said.
Zavodovski, which is about is about 1,200 miles from the nearest permanently inhabited settlement, is rarely visited by scientists because it’s so remote and extreme.
Zavodovski Island is a harsh, uninhabited volcanic island. (Photo Credit: John Dickens via CNN Newsource)
To reach it, BAS researchers set off from the Falkland Islands and navigated rough seas for two weeks. At points, they were forced to shelter in fjords from raging storms, before they eventually reached the only part of the island where the cliffs and swelling currents are gentle enough to allow people to scramble onto land.
They set up camp on the rocks and spent three days tracking and surveying the penguins using drones, aerial photography from a British plane stationed in the Falkland Islands and tracking devices fitted to the penguins.
Chinstrap penguin populations have experienced worrying declines in recent years. A 2020 study found drops of nearly 50% in some Antarctic island colonies compared to previous surveys in the 1980s. But, for a long time, it was believed Zavodovski Island had bucked this trend.
Instead, the BAS researchers found a sudden and dramatic decline on the island. It now has the highest rate of chinstrap penguin decline in the world. “We’re looking at annual population declines of around 7%,” Ratcliffe said, around two to three times the rate elsewhere.
The scientists ruled out a 2016 volcanic eruption as the cause, given the downward trend had started several years before and has maintained a steady pace across the years. They also found no evidence that competition for nesting space or the impact of regional krill fisheries were driving the fall in numbers.
They determined the most plausible cause is fossil fuel pollution, which is heating the ocean and disrupting the chinstraps’ key food source krill, which rely on sea ice for food and shelter. As warming forces the krill southward, the penguins can’t follow because the water is too icy for them.
The chinstrap penguin “is quite a specialist species that’s got a very limited global range, and that range is getting squeezed,” Ratciffe said.
There is some good news in the study. The scientists found the island’s macaroni penguin population increased by 28% between 2011 and 2016, after which it has stayed stable.
A macaroni penguin pair on South Georgia, an island in the the South Sandwich Islands chain. (Photo Credit: Alastair Wilson via CNN Newsource)
Their increase adds weight to the climate change theory, Ratcliffe said. Macaronis are happy in warmer water and have a more varied diet, so are not as reliant on the diminishing krill.
The scientists suggest that the chinstraps’ precipitous decline on Zavodovski Island, coupled with falls in other parts of Antarctica, may push them into the endangered category on the Red List of Threatened Species produced by the International Union for Conservation of Nature. They are currently designated as a species of least concern.
The findings are “really worrying news” for chinstraps as the South Sandwich Islands were thought to be their stronghold, said Noah Stryker, an ornithologist and author who was not involved in the research. “What strikes me about this study is how rapidly things are changing,” he added.
Peter Fretwell, a BAS researcher who specializes in remote sensing of penguins said the study is yet another example “of a warming climate impacting even the most remote parts of our planet. The South Sandwich Islands are far from any humans, home to almost a third of the world’s chinstrap penguins — but not even they can escape the impacts of climate change.”
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