Media playback is unsupported on your device

On patrol protecting the 'first crane egg in 400 years'

21 May 2013 Last updated at 09:18 BST

The first crane egg in southern Britain in more than 400 years has been laid by a nesting bird.

The Great Crane Project has been rearing cranes and reintroducing them to the West Country since 2010.

The egg is considered to be so precious, it even has a round-the-clock guard to protect it.

John Maguire reports from Slimbridge, Gloucestershire.