Emperor penguins are more dependent on fixed breeding sites than many other seabirds. However, new analyses of decades of satellite imagery show that some colonies are surprisingly flexible in their response to the loss of sea ice. They change their locations and even use icebergs or ice shelves as temporary breeding sites.
Emperor penguins rely on stable sea ice for their reproduction. The birds gather there during the Antarctic winter, lay their eggs and raise their chicks. If the ice breaks up too early, before the chicks have developed their waterproof plumage, an entire breeding season can be lost.
A new analysis of decades of Landsat satellite imagery now paints a more nuanced picture. Researchers have been able to trace the history of 18 emperor penguin colonies further back than previously possible. On average, the colonies studied had existed for around 17 years longer than earlier observations had suggested.
The colony near Smyley Island in the Bellingshausen Sea is particularly impressive. Satellite images show emperor penguins there as early as 1989 – around two decades earlier than previously documented. Today, the colony numbers several thousand birds.
Yet Smyley Island also demonstrates just how dangerous unstable sea ice is for the penguins. In 2022, there was likely a complete failure of the breeding season there. Nevertheless, the colony did not disappear. The penguins relocated and made use of areas near stranded icebergs, amongst other places. As late as December 2025, the colony was still visible in satellite images.
Icebergs as alternative habitats
Similar adaptations have been observed in other colonies. Emperor penguins at SANAE, Mertz and Astrid responded to ice break-ups and the loss of suitable sea ice by temporarily relocating to icebergs, ice shelves or newly formed ice patches.
This is particularly evident in the SANAE colony. Following a major calving event in 2011, the penguins relocated their breeding site by around eleven kilometres. They later returned to their original area.
The observations show that emperor penguins are apparently able to choose their breeding sites with greater flexibility than had long been assumed. Satellites such as Landsat now make it possible to track such changes over decades. The colonies are often recognisable in the images by large brown patches of guano on the otherwise white ice.
No cause for complacency
However, the emperor penguins’ adaptability does not mean that climate change has little impact on them. Alternative breeding sites may help in the short term to compensate for the loss of a specific area of sea ice. But they are no substitute for sea ice that remains stable for months on end.
Several poor years in succession are particularly dangerous. Repeated breeding failures could severely reduce populations in the long term, as there would be hardly any chicks hatching for years on end.
The new observations thus reveal two sides of the same story: Emperor penguins possess an astonishing ability to respond to changes in their icy environment. Yet even this flexibility has its limits if Antarctic sea ice continues to retreat in the long term.
Rosamaria Kubny, PolarJournal