Climate change causes arctic geese to take different routes

Global warming is a challenge for many migratory species living in the Arctic, including migratory birds. Because the seasonal development of the plants changes, the food supply also changes. "Such species can only survive if they adapt their migration, breeding times and range," writes an international research team led by Jesper Madsen from the Danish University of Aarhus in the journal Current Biology. The researchers are now describing such an adaptation for the pink-footed goose (Anser brachyrhynchus), which is native to Northern Europe.

For more than 35 years, the group has been observing a population of almost 80,000 pink-footed geese in their breeding area on the Norwegian archipelago of Spitsbergen. The traditional migratory route of these birds is a narrow corridor from Spitsbergen to their gathering places in Norway and then to wintering in an area stretching from western Denmark along the North Sea coast to the Netherlands and Belgium.

However, over the past 20 years, animals from this population have repeatedly been sighted in Sweden and Finland, i.e. beyond their actual route. In order to determine their migration routes, the researchers in Finland equipped 21 pink-footed geese with GPS transmitters. The result: half of the birds did not fly from their winter quarters to Spitsbergen via Norway to breed.

Instead, these geese migrated via Sweden and Finland to the Novaya Zemlya archipelago in northern Russia, almost 1,000 kilometers east of Svalbard. There they built their nests on the island of Sewerny. This route leads across the Bay of Lübeck on the German Baltic Sea coast.

This was a "real surprise" for the researchers, Madsen is quoted as saying in a statement from the journal, especially since the route to Novaya Zemlya is almost a quarter longer than that to Svalbard. The team also observed that some geese deliberately switched from their original flight route to the new route. This indicates that the animals learn socially from each other.

"It is extremely fascinating to observe such a rapid development of new breeding areas and migration routes of a bird species that is considered to be very traditional in its behavior and use of its site," says lead author Madsen.

The new route was established within 10 to 15 years, and a new population of geese developed in Novaya Zemlya. Between 2000 and 2020, the number of animals there increased by 24 percent annually. The research team estimates that the population now includes up to 4,000 animals.

Overall, the brood in northern Russia also seems to be more successful. According to the researchers, the fact that the birds can live well in Novaya Zemlya has something to do with climate change. The team writes that it was originally too cold for the geese there. Spring temperatures in the region are now similar to those on Svalbard at the turn of the millennium.

How the pink-footed geese got to their new breeding grounds in northern Russia is unclear. The researchers suspect that the birds may have followed taiga bean geese (Anser fabalis fabalis), which also overwinter in Denmark and migrate to Sewerny Island to breed. It is also possible that some pink-footed geese drifted off during their flight across the Barents Sea due to strong westerly winds and accidentally landed in Novaya Zemlya.

The researchers want to observe the geese more closely in their new breeding area in the future. However, their study already shows that social herd or swarm animals such as migratory birds can actively learn from each other and thus adapt quickly to climatic changes. And that, according to first author Madsen, gives hope for an "ecological rescue in times of very radical environmental changes".

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