Britain usually attracts over five million birds each winter from cooler places such as Greenland, northern Europe and Siberia – but the number is falling.
Warmer winters mean that some yearly visitors are choosing not to fly as far as Britain because they can find suitable conditions closer to home, the RSPB 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," said RSPB Conservation Director Mark Avery.
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