Conservationists at the Slimbridge Wetland Centre in Gloucestershire have set up a round-the-clock guard to protect the first crane egg laid in the South West in over 400 years.
Hunting and the loss of wetlands drove cranes to extinction in Britain.
For the last three years, the Great Crane Project has been rearing the birds in captivity and reintroducing them to the West Country.
The egg at WWT Slimbridge is the first known to be laid by cranes released by the project.
Bird spotters are able to see the male and female cranes taking turns at sitting on the nest.