The bird has not been seen in Britain since 1832

The aim was to transfer 30 great bustard chicks from Russia to start a 10-year project in Wiltshire to re-establish the species.

But the conservationists involved flew back to Heathrow Airport from Saratov on Wednesday without the chicks.

A spokesman for the British Great Bustard Group said there had been a problem with official paperwork.

Dr Patrick Osborne of the group, said: "There are problems with the paper - the number of licences which are needed at both ends - in Britain and in Russia.

Salisbury Plain

"A project like this is really quite extraordinary and we've hit the problem.

"Although the licence has been approved, it needs a signature and that signature has to come from someone who hasn't yet been appointed."

Eggs had been collected in Russia from nests threatened with destruction.

Forty chicks of around one or two weeks old were to be taken to Salisbury Plain for rearing.

The great bustard was hunted to extinction in Britain in the 1830s, partly because its meat was so sought after by the nation's chefs.