Four captive-bred northern bald ibis chicks have been sent from Chester Zoo to Jerez in Spain, where they will soon be released into the wild as part of an effort to reintroduce the species.
The bird was once widespread, from North Africa to Central Europe, but is now almost extinct in the wild.
In Europe, there have been no northern bald ibis in the wild for 300 years.
The Chester chicks will join others, from zoos around Europe, for a bonding period before they are set free.
"It's amazing enough working with these remarkable birds in the zoo, but to be part of a successful reintroduction programme is something extra special," said Lauren Hough, a bird keeper at the zoo.
"We hope that by reintroducing birds into the wild, they will go on to breed and boost the wild population themselves, securing the future of the species."
At present only about 500 of the birds can be found in the wild, largely in a population in Morocco.
A second, tiny group remains in Syria, where the birds are threatened by the advance of IS militants.
They have disappeared from Europe due to habitat loss and hunting of their chicks and eggs.
Chester Zoo currently houses 28 northern bald ibis, a "safety-net population" the zoo has cared for since 1986.
The latest four chicks from Chester are joining an international conservation effort, which has already seen wild numbers of the birds begin, slowly, to recover.
They will live in a holding aviary at Jerez Zoo in southern Spain until they are released, possibly in late November.