Devon and Cornwall barn owls threatened by weather

Barn owl (pic: Kevin Keatley)
Image caption A combination of cold winters, dry springs and wet summers could have affected barn owl numbers, said the trust

A decline in barn owl numbers in Devon and Cornwall has been predicted by a bird charity after two years of "severe and exceptional" weather.

The Barn Owl Trust fears snow and freezing conditions, dry springs and wet summers have affected numbers.

Every 10 years it monitors hundreds of sites throughout Devon and Cornwall.

In 2003, it recorded up to 470 pairs in Devon, and in 2004, up to 361 pairs in Cornwall, but fears the 2013/2014 survey will show a decline.

During the last survey, Devon and Cornwall had about 18% of the UK population of barn owls, the trust added.

David Ramsden, the senior conservation officer, said: "We anticipate that barn owl numbers are currently very low due to a combination of severe winter weather, exceptionally dry springs and wet summers."

He said he anticipated the snow and freezing conditions of recent winters would have prevented the owls from getting enough food.

The winter of 2010/11, in the UK, was the second-coldest since 1985/86, with the coldest December in more than 100 years, the Met Office said.

Image caption Harsh winters prevents barn owls from feeding on rodents living beneath the snow

According to the British Trust for Ornithology, more than 100 barn owls were found dead across the UK in December 2010 alone - three times the usual number ornithologists would expect.

Mr Ramsden said: "Barn owls evolved in a much warmer climate than we have in the British Isles and are not well insulated.

"They are also incapable of storing much body fat and easily starve during severe winters."

Starving young owls

The birds feed on rodents, especially voles.

The spring of 2010 was the driest in the UK since 1984 and ranked equal-eleventh-driest from 1910, the Met Office added.

Mr Ramsden said: "The weather inhibited grass growth and it was likely to have suppressed field vole numbers.

"As a consequence, those owls that survived the winter either failed to lay eggs or abandoned them."

In 2010, the dry conditions resulted in an average brood size - number of young owls in the nest - of 2.3 compared to an average of 2.9, he added.

Mr Ramsden said: "In both 2010 and 2011, dry springs were followed by wet weather starting in June 2010 and July 2011."

Image caption During the surveys the trust looks for the birds, their pellets and vacated nests

Barn owls have soft feathers which are not very waterproof and prevent the species from hunting well in rain.

"Routine nest inspections in 2010 and 2011 revealed unusually large numbers of nests with owlets [young owls] dead or dying due to lack of prey delivery by the adults," he added.

In 2013, the trust plans to survey about 1,400 sites in Devon and 1,000 in Cornwall the following year.

The trust will look for owl signs including vacated nests and pellets - the thumb-sized lumps of hair and bone that owls regurgitate after feeding.

Mr Ramsden said: "One of the great advantages of visiting all known barn owl sites is that we can identify opportunities for the creation of field vole habitats and erect nestboxes where they are most needed."

He added that he hoped 2012's weather would be better for barn owls which could help populations in both counties after the conditions in the past two years.

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