Conservationists dressed in crane costumes have helped bring the graceful grey birds back to Britain's wetlands after they were hunted to near extinction as a delicacy in the Middle Ages.

The Royal Society for the Protection of Birds (RSPB) said the hand-rearing of 93 cranes in Somerset, southwest England, had been "instrumental" in bringing the total number of cranes in Britain to 160.

"It's an incredibly useful technique. It allows you to act as a surrogate parent," Damon Bridge, one of the conservationists who reared chicks from eggs as part of the "Great Crane Project", told AFP.

Wearing grey body suits, Bridge and other bird enthusiasts socialised with and fed the chicks with devices shaped like a crane's head and painted with a bird's face in a programme that ended in 2014.

Bridge said the aim was to prevent chicks from "imprinting" on humans before being released into the wild so they don't rely on people to feed them.

The chicks that were reared in this way have survived in the wild and have now themselves begun breeding.

"The population has probably grown to a size where it has reached a critical mass," said Bridge.

The Great Crane Project is a partnership between the RSPB, the Wildfowl & Wetlands Trust and the Pensthorpe Conservation Trust.

"It's a dream come true... Cranes are well on track to become a true conservation success story for the UK," said Rebecca Lee, principal conservation breeding officer at the WWT.