Record number of polar bear visits to eiders nesting on islets on Spitsbergen

The reduction of sea ice is forcing polar bears to search for food on land. This summer, researchers have recorded an unusually high number of polar bear visits in Kongsfjorden, an important breeding area for common eiders. This could have consequences for bird life.

This article was first published at nina.no

One polar bear a day

Kongsfjorden is located in northwestern Spitsbergen and serves as a breeding area for a wide range of seabird species. Based at the Sverdrup Station in Ny-Ålesund, researchers are able to observe the birds and other life in the fjord at close range. During the period from 4 June to 4 July this year, 30 polar bear days were recorded in Kongsfjorden, coinciding with the time when common eiders are nesting and incubating their eggs. On average, this means that one polar bear was present each day during this period.

“This is the highest number we have ever recorded”, say NINA researchers Sveinn Are Hanssen and Børge Moe following this year’s fieldwork in Svalbard.

Only one brood escaped

In collaboration with the Norwegian Polar Institute, the researchers monitor the eider population and document how it is affected by polar bears. With one exception, images from all eleven nest cameras showed eider eggs being eaten by polar bears. The last nest camera also recorded a polar bear visit but the eggs had hatched in time for the female eider to leave the nest with her ducklings before the bear arrived.

The researchers confirmed what the photographs showed when they surveyed a large number of nests to assess hatching success. Very few female eiders had managed to raise young in Kongsfjorden this year.

Less sea ice drives polar bears ashore

“The reduction in sea ice reduces the polar bear’s ability to hunt ringed seals and bearded seals, and the bears increasingly have to search for harbour seals and alternative food sources on land,” says Jon Aars, polar bear researcher at the Norwegian Polar Institute.

Together with bird researchers, he has shown that the summer occurrence of polar bears on land has increased in step with the decline in sea ice around Spitsbergen over the past 30–40 years, and that this may have consequences for colonial nesting birds.

Is the population declining?

The common eider is a long-lived species that can tolerate poor breeding success in some seasons. Hanssen explains that polar bears have, however, often caused a reduction in breeding success over the last ten years and is now asking whether the eider population may begin to decline.

This year’s surveys show that the eider population in Kongsfjorden has indeed decreased by approximately 28% since 2025.

“It is not unlikely that we are beginning to see the effects of reduced recruitment”, says Sébastien Descamps, seabird researcher at the Norwegian Polar Institute.

“This is an important example of why long-term monitoring and research are essential for understanding climate change and the changes occurring in Arctic ecosystems”, adds Moe.