Unfortunately, the great bustard was regarded as a delicacy

But the key to its survival could lie in a water pistol used to show the world's heaviest flying bird it still faces predators - like the fox.

Keepers will allow the bird to see a fox - and then squirt it with water to make the bird link the animal with danger.

The support group will also place a stuffed fox in the birds' pen to aid recognition.

The chicks are being kept in quarantine to be prepared for release on Salisbury Plain.

David Waters, of the British Great Bustard Group, said: "The dream is to see a self-sustaining population when they're out there and producing their young - but just to see them out there would be a big milestone."

Farming and hunting killed British Bustards in 1830s They stand to the height of an adult Roe Deer They can be more than a metre long and upwards of 15kg About 40,000 Bustards are in Spain, Portugal, central Europe, Russia and central Asia Their alarm call is a short, nasal sound similar to a bark

The great bustard, which can weigh around 15kg, once thrived in the UK.

Unfortunately the bird was regarded as a great delicacy in Britain and the last one was shot and eaten in 1832.

Plans to hatch chicks in Russia and bring them to Wiltshire were expected to come to fruition earlier this year, but the completion of the project was delayed by paperwork on the Russian side.

The chicks were flown in for release under a joint project between the Salisbury-based Great Bustard Group and the University of Stirling, working with Russian partners.

The birds were eventually granted an export licence when the UK government stepped in.

After an initial check at a UK airport's animal reception centre, they will have to spend a month in quarantine.

They will then be moved to "soft pens", where they will become accustomed to outdoor conditions while still being safe from predators.