A cold March and a wet May combined to kill off parent birds and create appalling breeding conditions for survivors, the Barn Owl Trust said yesterday. Attempts by the birds to recover by raising late broods were ruined by repeated downpours last month.

Fewer than one in four regular breeding sites has been occupied this year in much of the country, and in Shropshire the figure fell to one in twelve.

“It’s the worst year I’ve ever known,” David Ramsden, the head of conservation at the trust, said. He blamed changing weather patterns caused by global warming. “We were very optimistic things were generally picking up but this year has been a huge setback. We aren’t just talking about a few less pairs, we are talking about an incredible number less.”

Farmers and other barn owners have been so alarmed at the struggle the birds have faced to survive that they have been leaving out food.

Barn owls are harbingers of death in folklore and literature. Shakespeare, Byron, Jonson, Wordsworth and Keats all linked the bird with death or misery.

Now the population has slumped well below the 4,000 pairs recorded in Britain in 1998. It had fallen in England and Wales by 69 per cent from 1932, when 12,142 pairs were recorded, to 1985 when 3,778 pairs were surveyed.

Population levels were thought to have stabilised from the 1980s and, since 1998, it was believed that numbers were recovering. But this year’s figures have set back conservation efforts by at least a decade.

Mr Ramsden added: “There may be as few as a thousand pairs breeding this year in the whole of the UK. That’s catastrophic. The numbers are lower than ten years ago. Almost every year has record-breaking weather and prolonged extreme conditions are bad news for barn owls. The thought that climate change may significantly hinder the recovery of this national treasure is a huge worry to those concerned with barn owl conservation.”

Mr Ramsden has been monitoring sites in Devon and collating findings from surveys elsewhere. In Devon only 15 of the 72 regularly monitored nest sites were occupied this year. Most or all would normally be used by the birds and their absence has been repeated in many other counties. A cold March meant that the small mammals on which barn owls prey, particularly voles, were in short supply. Many adults starved to death. The number of dead owls reported in early spring was three times higher than usual.

Persistent rain in May forced the birds to restrict their hunting because the feathers that enable the owl to fly silently get waterlogged easily.

A further sign of an appalling year is the lack of reports this month of owls being struck by vehicles. About 75 per cent of barn owls that die in their first year are killed in this way.

Monitors for the British Trust for Ornithology also reported disastrous results for the owl this year. David Leech, for the BTO, said that the bird had suffered particularly badly in the South West.

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