A Norfolk-based research organisation has reached the halfway mark of Britain's biggest ever stocktake of birds.Since the British Trust for Ornithology (BTO) launched the British Bird Atlas project two years ago, 16,000 volunteers have submitted more than three million observations.

A Norfolk-based research organisation has reached the halfway mark of Britain's biggest ever stocktake of birds.

Since the British Trust for Ornithology (BTO) launched the British Bird Atlas project two years ago, 16,000 volunteers have submitted more than three million observations.

But officials from the Thetford-based body are calling for more volunteer birdwatchers to get involved in the scheme, which is set to run until 2011.

Dawn Balmer, atlas organiser at the BTO, said the research was providing a valuable insight into the changes of species distribution across Britain and Ireland.

'We are on target to achieve our coverage aims, with 68pc of our timed counts completed for winter and 65pc completed for the breeding season.'

'Although this sounds very positive, there are still many areas that need a considerable amount of effort over the next two years. These tend to be areas where fewer people live, remote areas or difficult terrain to cover,' she said.

For more information, visit www.bto.org.uk.