Climate change shifts migrating birds' wintering ground

Three species of migratory duck have shifted their wintering grounds northward in response to increasing temperatures, say scientists.

The birds - the tufted duck, goosander and goldeneye - are common in Britain and Ireland during northern Europe's winter.

But their numbers in these countries have shrunk in the last 30 years.

According to the findings, published in the journal Global Change Biology, many now stop short on their annual journey.

Gathering and analysing data from the three-decade-long International Waterbird Census, the researchers found many birds were staying closer to their summer breeding grounds all year round.

At the northern end of their migratory flyway, in Sweden and Finland, there were approximately 130,000 more of the ducks in 2010 than in 1980.

On the southern end - in Britain, France, Ireland and Switzerland - numbers have dropped by about the same amount.

According to Richard Hearn from the Wildfowl and Wetlands Trust (WWT), who was involved in the study, this represented a loss of between 45 and 60% of the population in Britain and Ireland.

"It makes more sense for the birds, because they don't have to embark on that very energy-intensive journey," he explained.

This "huge" shift he said was caused by increasingly warmer European winters. The researchers drew this conclusion by examining temperature data gathered from the same areas of Europe over the last three decades.

"Early winter temperature in south Finland," Dr Hearn said, "increased by about 3.8C between 1980 and 2010."

This shift in migration is known as "short-stopping", whereby Arctic-breeding species that head to milder climates for the winter find they no longer need to travel so far for the unfrozen lakes that allow them to find food.

"This may have implications for their conservation, because birds are making less use of the areas that were designated to protect them," said Dr Hearn.

He added that the findings were a warning sign of the implications of a warming climate.

"These northern shifts can't go on forever, because the birds will simply run out of habitat," he said.

Andy Musgrove, head of monitoring at the British Trust for Ornithology, said this was "an important paper" adding to a growing body of evidence concerning the response of wildlife to a changing climate.

"All species are adapted to live in particular environments and when conditions change, then species will respond if they can," he said.

"What is interesting with migratory birds is how rapidly they are able to change their distributions, as a result of their ability to cover long distances to find suitable conditions.

"It is likely that the decline in UK wintering numbers of goldeneye, for example, is linked to the increase in Scandinavia.

"This is not always the case however, and for other species such as Bewick's swan and velvet scoter, it looks like declines in the UK are matched by those elsewhere across Europe.

"Such different cases really emphasise the importance of international cooperation in the monitoring of birds and other wildlife."