A scientist from Gloucestershire says migratory waterbirds have shifted their wintering patterns in response to changes in the world's climate.
Richard Hearn, head of species monitoring at the Wildfowl & Wetlands Trust in Slimbridge, says more birds than ever are being forced to migrate in an increasingly north-easterly direction.
A report published in the journal Global Change Biology found a strong link between changes in the numbers of goldeneyes, tufted ducks and goosanders wintering across northern Europe and changes in temperature in early winter.
Mid-winter numbers in Finland and Sweden are now more than 130,000 higher than three decades ago. While on the southern edge of the distribution in France, Ireland and Switzerland, numbers have dropped by nearly 120,000.
Mr Hearn warned conservation tools need to be flexible to adapt;
"Our world is changing rapidly. This means more monitoring...it also means maintaining a coherent network of protected areas throughout Europe, and altering their management in response to the changing mix of wildlife that uses them."