Climate change warning over migrating birds

But the overall number of waterbirds spending the winter in the UK in the last three decades has doubled, The State of the UK's Birds 2006 report says.

The RSPB says there has been a decline in populations of the Greenland white-fronted goose, European white-fronted goose, shelduck, mallard, pochard, ringed plover, dunlin and turnstone.

Some birds, which are normally attracted to spend the winter in Britain and Ireland because of the relatively mild climate, are no longer forced to fly as far as the UK to find suitable conditions.

The report found the trend was "particularly noted" in Northern Ireland, with declines of pochard and Bewick's swan.

Bird experts say the precise reasons for the decline of each species vary, but a common theme appears to be climate change.

Dr Mark Avery, the RSPB's conservation director, said: "The UK has had both the perfect climate and perfect habitats for these birds, but the evidence is growing that climate change impacts are starting to bite.

"Sea level rise and warmer winters are reducing their numbers, undermining our importance for birds."

Conservationists say the UK receives more than five million ducks, geese, swans and wading birds, from northern Europe, Greenland, Siberia and Arctic Canada, every winter.

These birds are attracted to spend the winter in Britain and Ireland because of the relatively mild climate and ice-free conditions.

The report, which monitors populations in 39 species of waterbird, found numbers of wading birds including the black-tailed godwit and the avocet, have increased markedly since the late 1970s, largely because of conservation action.

Dr Baz Hughes, head of species conservation at the Wildfowl and Wetlands Trust, said: "Every winter, the UK's estuaries, marshes and wetlands throng with the arrival of ducks, geese, swans and wading birds, making the UK one of the most important countries in the world for some of these birds.

"However, we are becoming increasingly concerned about the declining numbers of some populations.

"While some are simply taking advantage of milder winters by staying on the continent, others like the Greenland white-fronted goose, are in real and rapid decline.

"Conservation action is needed urgently to reverse these declines."

Dr Mark Rehfisch, of the British Trust for Ornithology and one of the report's authors, said: "For over 30 years, teams of volunteers have braved the worst conditions a British winter can muster to count the numbers of birds visiting each of the UK's most important sites for wetland birds.

"This huge effort has not only contributed to one of the best sources of bird information in the world, it is also vital in helping us to understand climate change impacts on the natural world."

Natural England's chief scientist Tom Tew said: "Sympathetic and effective management of the UK's world-renowned network of internationally important waterbird sites and the surrounding countryside is vital if we are to minimise the adverse impacts of climate change on our overwintering birds.

"Agri-environment schemes have a crucial role to play by encouraging land management practices that benefit birds and other wildlife."