Farmers are being urged to help wildlife pushed to the brink of a crisis by Britain's big freeze. Cold winter weather was potentially the greatest single wildlife killer of the new millennium, said the RSPB.
It is urging farmers to spare a thought for threatened birds, such as corn buntings and yellowhammers, on their land.
Farmers could help by putting out supplementary food, especially in the form of grain tailings or residues from last year's crops, near known bird territories.
The RSPB is also urging people not to disturb flocks of wetland birds, including ducks, geese, swans and wading birds.
Disturbance causes these birds to expend energy they cannot replace pushing them to the brink, said Mark Avery, RSPB conservation director.
"The extremely hard winter spanning 1962 and 1963 was arguably the single event that had the greatest impact on Britain's wildlife within living memory.
"With the icy weather predicted to last at least another week, this winter could be the single greatest wildlife killer of the new millennium.
"Farmland birds were often at their most vulnerable in the winter, said Dr Avery.
"Food is most scarce, so the continued bitterly cold weather and snow cover on the ground could have a potentially devastating impact.
"Putting out grain tailings is one simple thing farmers can do that is proven to make a difference to birds' survival through the winter."
It was likely that the legacy of this hard winter would be seen in bird populations for years to come, Dr Avery warned.
The RSPB's switchboard was becoming clogged with people reporting sightings of unusual birds turning up in gardens, he added.
Callers had reported sightings of woodcock, snipe and grey wagtails - all birds not normally seen in gardens.