World's largest penguin colony loses half a million birds
A 63% fall in Chinstrap Penguins has cost Zavodovski Island its global record and changed the balance of its seabird community.
Zavodovski Island has lost more than half a million Chinstrap Penguins since 2011, a decline large enough to remove its status as the world's biggest penguin colony. New counts indicate that the island's Chinstrap population has fallen by about 63%, while Macaroni Penguins have increased by around 28%.
The remote volcanic island lies in the South Sandwich Islands, roughly 2,000 km from the nearest permanent settlement. In 2011 it held an estimated 600,000 Chinstrap Penguins and about 90,000 Macaroni Penguins, making it an exceptional concentration of breeding seabirds.
Researchers combined aerial imagery, ground observations and earlier survey material to reconstruct the change. Their Current Biology paper, Population declines and changes in community composition at the world's largest penguin colony, was published on 7 October.
The decline appears to have begun by 2011 and continued steadily. That pattern argues against the 2016 eruption of Mount Curry as the main cause. Ash and lava affected part of the island, but the losses were already under way and were not concentrated in the area most heavily covered by volcanic material.
Our study is another example of a warming climate impacting even the most remote parts of our planet.
Peter Fretwell, British Antarctic Survey
The authors instead point to changing food availability as the most plausible explanation. Chinstrap Penguins depend heavily on Antarctic krill and forage in cooler water north-west of the island. As the Scotia Sea warms, krill distribution is expected to move south towards the Weddell Sea, beyond waters that breeding birds can readily exploit from Zavodovski.
Macaroni Penguins eat a wider range of prey, including fish and amphipods as well as krill. Their increase suggests that neither the eruption nor a simple island-wide shortage of nesting space explains the contrasting trends. The study also found little support for direct food competition between the two penguin species.
The British Antarctic Survey says Zavodovski now has the fastest documented Chinstrap Penguin decline in the world. Cape Adare in the Ross Sea, dominated by Adelie Penguins, is thought to have taken over as the planet's largest penguin colony.
The loss changes more than a record. Penguins move nutrients from sea to land, support scavengers and form part of a food web built around krill. Lead author Professor Norman Ratcliffe compared ecosystems to a Jenga tower: removing components increases the chance of wider instability.
The authors say the rate of decline could affect the global conservation assessment of Chinstrap Penguin if comparable losses are confirmed elsewhere in the South Sandwich Islands. The present study covers one exceptionally important island, so it does not by itself establish the trend across the species' entire range.
Chinstrap Penguins remain numerous globally, but abundance can conceal rapid losses at major colonies. Further surveys of Candlemas, Visokoi and Saunders islands are needed to establish whether the Zavodovski pattern is local or part of a broader change across this sector of the Southern Ocean.
8 Oct 2026
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