Fewer birds will migrate to the UK each year as warmer temperatures caused by climate change will encourage them to spend winters closer to home, a report warned today. Research from the Wildfowl and Wetlands Trust (WWT) has shown a big drop in the numbers of ducks, geese, swans and wading birds migrating to UK wetlands in winter.

The report, published by the WWT, the British Trust for Ornithology and the RSPB, says climate change and milder winters may cause many birds to shorten their migration routes and stay closer to their breeding grounds. This means that many traditional wetland sites in Britain will miss out on the annual spectacle of migratory winter birds.

Many birds arrive in the UK from the colder regions of the Arctic circle such as Canada, Greenland, Iceland, Scandinavia or Russia. They spend either the winter in the UK or stop for food and rest along migratory routes. The 2006-07 UK waterbirds survey identified 143 sites around the UK that are of international importance for 43 species of waterbirds, either during the winter or migration periods.

Figures showed that the numbers of Bewick's swan were just half of those recorded last year, the lowest for 30 years. Numbers of European and Greenland white-fronted geese continued to suffer long-term declines, while the numbers of dunlin — one of the UK's most abundant waders — was the lowest since 1970.

The numbers of ducks such as wigeon, teal and shoveler all fell, with wigeon suffering a decline of one-fifth, the report showed. Redshank — a type of wader — have declined for the third year running, reaching its lowest level for 20 years. The UK's two species of godwit — types of wading bird — showed differing trends. The black-tailed godwit reached its highest level, while the bar-tailed godwit reached its lowest level to date, after a five-year decline.

The report found that some species of waterbirds are increasing, with avocets reaching record numbers. Dr Debbie Pain, the director of conservation at the WWT, said: "At this time of the year, 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."

The report said more research was needed to establish whether more birds are altering their migration routes or whether there has been a dramatic collapse in numbers worldwide.

It identified five sites in the UK that are of international important for 12 species of bird or more. These are the Ribble (16 species); The Wash (16 species); the Humber (12 species); Morecambe Bay (12 species) and the Thames (12 species).

The Wash is the most important site in the UK for six species — the dark-bellied brent goose, the grey plover, lapwing, knot, black-tailed godwit and bar-tailed godwit.

The Thames estuary complex is the most important site in the UK for ringed plover, and Morecambe Bay is the most important UK site for curlew, oystercatcher and lesser black-backed gull, the researchers found.

(Por Jessica Aldred, The Guardian, 17/11/2008)