Ornithologists who have spent the last three years researching the number of barn owls in Britain say the bird is still very scarce.

Karen Bauman: Conservationists say even the smallest steps can help protect the species

But they say their findings give grounds for hoping that the species' numbers may have stabilised after years of decline.

The researchers, from the British Trust for Ornithology and the Hawk and Owl Trust (Hot), say the owl is still a rarity and needs all the help it can get.

They found an estimated 4,000 breeding pairs in the UK - roughly the same as the numbers found in a survey in the mid-1980s.

Colin Shawyl: The news is bad, but it is not as bas as it could have been

More than 1,000 specially trained volunteers looked in 900 randomly-selected areas of the country for signs of breeding owls.

They searched both in winter and summer over the three-year period, to allow for natural variations in owl numbers caused by fluctuations in food supplies.

Each volunteer contributed about 30 hours' work, and their total efforts amounted to six-and-a-half working years.

Exhaustive research

The organisers say this makes the survey possibly the most detailed and labour-intensive for any single British bird.

In the 1930s there are thought to have been about 12,000 pairs of barn owls in England and Wales alone.

The findings from the 1980s survey represented a fall of about 70%.

There has been a loss of nesting sites

Ornithologists concluded that the main threats to the species were the loss of feeding habitat and nesting sites, changes in farming practice, harsh winters, and a growing toll from road deaths.

In the years since then the Hot has been active in trying to create and restore rough grassland feeding places.

It is also working to provide artificial nest sites where natural sites in barns and trees have become scarce.

Barn conversion a problem

Work carried out in parallel with the latest survey shows that at least 30% of nest sites in buildings have been lost since the 1980s survey, mainly through the conversion or demolition of barns.

About 30% of nesting sites in trees have also been lost, because the trees have suffered wind damage or else have been felled.

Harsh winters make survival more difficult

The co-ordinator of the most recent survey said it showed not only that the barn owl was still very scarce, but also that it "is clearly a species which is still under threat in many areas as nest sites and suitable hunting habitats continue to be lost".

The researchers did find that barn owl densities in East Anglia were higher than those found in the 1980s.

That is an area where bodies like the Hot have been working over the last 15 years with farmers and landowners to create rough grassland margins and provide artificial nest sites.

Corridors needed

The Hot says it shows the difference its work is making.

It wants to create a countrywide network of grassland corridors to help the birds.

It is also spending three years studying the impact on the owls of new roads at a site in Somerset.