Warm winters change migration patterns

Shall we go, or shall we stay? Gulls at a landing stage on Lake Lucerne Keystone

Many water birds which usually migrate south from Switzerland have stayed put this winter, while birds from more northerly areas have not turned up, according to the preliminary results of this year’s first aquatic bird census, released on Friday.

Michael Schaad of the Swiss Ornithological Institute, which organised the census in January, told the Swiss News Agency that there had been an overall shift north, because of the unusually warm winter. He explained that birds move south when food becomes scarce. The cold itself does not bother them.

Usually about 500,000 aquatic birds from northern Europe overwinter in Switzerland. This year there are barely 1,000 common goldeneyes; usually nearly 10,000 fly down from the Arctic. The number of common gulls is about a fifth lower than the average of the last 50 years, with only 1,000 birds.

Although the census counted 100,000 tufted ducks, that is about a third fewer than in most winters. Some birds which only ever appear in small numbers have not been spotted at all.

On the other hand, 30,000 red crested pochards were counted, the largest number for 50 years, and the number of great crested grebes, more than 40,000 individuals, was a third more than average.

Schaad said the shift northwards was a trend that had been developing over the last 30 years, as temperatures in early winter have risen by nearly four degrees.

But it poses a problem to bird protection bodies: the new migratory behaviour means that the protected status of the overwintering areas of aquatic birds all over Europe will have to be reconsidered.

The census of aquatic birds has been carried out in Switzerland since the 1950s, as part of a major European monitoring programme.