Little egrets have pushed further north into the UK during the winter months
Climate changes are behind a dramatic shift in the numbers of wetland birds visiting the UK, a study suggests.
The numbers of birds, including ring plovers and pochards, wintering in the UK have fallen by around a half in the past decade, according to the RSPB.
However, other species such as avocets and little egrets have increased their numbers during the winter months.
The wildlife charity said mild winters meant some species did not have to travel as far for suitable conditions.
The "Waterbirds in the UK 2007/08" report found little egrets have pushed further north into the UK, increasing their numbers by more than 800% over 10 years.
INCREASES IN WETLAND BIRDS
Little egret 811%
Whooper swan 135%
Black-tailed godwit 79%
Greenland barnacle goose 66%
UK winter figures over 10 years. Source: Waterbirds in the UK 2007/08 report
Numbers of ringed plovers and bar-tailed godwits wintering in the UK fell by 57% and 42% respectively.
Royal Society for the Protection of Birds (RSPB) spokesman Grahame Madge said: "Conditions have been generally mild in winter, notwithstanding this winter, and the birds are not having to travel so far."
Richard Hearn, head of species monitoring at the Wildfowl and Wetlands Trust, warned against assuming that changes in climate were the only factor.
"Climate-related changes in distribution have the potential to mask more serious conservation problems," he said.
RSPB conservation director Mark Avery said the study showed how important British wetlands were to birds migrating from abroad.
"The protection and wise management of our wetlands is a priority to ensure that they continue to provide a lifeline to bird populations in the face of climate change," he said.