Seeking answers in 'barn owl mystery'

Barn owls are a protected species

A Northern Ireland academic is seeking the public's help to find out the causes of poisoning in barn owls.

Dave Tosh of Queen's University is examining if rat poisons are turning up in animals which are not targeted.

He has appealed to the public in a bid to find out where barn owls roost and collect the pellets that gather there.

The number of barn owls in Northern Ireland is low and Mr Tosh is analysing their diet and if it is likely to expose them to rodenticides.

"Understanding the species' diet is important, as in the UK the vole is the most common prey item of the barn owl," he said.

"Unfortunately for the barn owl, the vole does not naturally occur in Ireland, so it must be eating something else.

"What that is, we don't know, but we could speculate that it is eating wood mice, house mice and brown rats.

A few examples of other predator species in which rodenticides have been found are kestrels, red kites, buzzards, stoats and polecats Dave Tosh

"It is therefore possible that rodenticides used to target these species are indirectly affecting the barn owl through its diet."

The barn owl population is thought to have declined in the UK by as much as 50% in the past 50 years.

"Although not thought to be the main reason for their decline, it is thought that rodenticides may affect the species breeding success," said Mr Tosh, who works at Queen's school of biology and biochemistry.

The incidence of rat poisons in barn owls across the UK has increased from 6% in the early 1980s to 40% currently.

While deliberate poisoning was rare, the Wildlife Incidence Investigation Scheme (WIIS) run by DEFRA investigated any incidents where it was suspected poisoning was the cause of an animal's death, said Mr Tosh.