The world's most threatened birds set up new nest in Gloucestershire

They are the most endangered birds on Earth but at the weekend a captive flock of young spoon-billed sandpipers began a new life at Slimbridge in Gloucestershire, the celebrated reserve of the Wildfowl and Wetlands Trust (WWT) on the Severn Estuary.

The small waders from Asia are renowned for their charming, flat-ended or "spatulate" bills, but in recent years they have taken on another distinction – they appear to be the fastest-declining bird species in the world, and now number fewer than 100 pairs, their population having dropped by 90 per cent in a mere decade.

They are vanishing because twice a year they make a giant, 5,000-mile migratory journey between their nesting grounds in the Russian Arctic and their wintering grounds in Bangladesh and Burma, and their "pitstops" – the Chinese and Korean estuaries and wetlands along the route of the so-called East Asian flyway, where the birds rest and feed – are disappearing, being swallowed up by reclamation schemes of the powerhouse Asian economies. They are also suffering from hunting pressure.

This summer, an Anglo-Russian expedition took 13 spoon-billed sandpiper eggs from the nesting grounds in Russia's Chukotka province. The aim is to form a breeding population to provide a safety net against extinction, should the wild population continue its dramatic decline.

The eggs were hatched in special facilities on site and the young chicks transported to Moscow. After a period in Moscow Zoo, the birds were sent to quarantine buildings at Slimbridge; at the weekend they moved out of quarantine into the special quarters that have been prepared for them.

Nigel Jarrett, WWT's head of conservation breeding, who helped lead the expedition to Russia, said: "These birds would normally range from the frozen Arctic to tropical coastal wetlands in South-east Asia, and despite being held in unnatural surroundings they have done very well.

"The site at Slimbridge is purpose-built and a little larger than the quarantine area. It is crucial we keep it warm because at this stage in the birds' lives they'd normally be in the tropics. In some ways we're going into the unknown but every day that passes is a success. The priority is to keep them alive and healthy so that eventually they can breed."

As the spoon-billed sandpiper is an iconic bird for anyone interested in wildlife, progress in attempts to save it is being followed by thousands worldwide. The captive flock will receive 24-hour care inside the new area where CCTV cameras let WWT staff watch the birds constantly. Footage from the cameras is also being broadcast to public screens at WWT.

Andre Farrar of the RSPB said: "It's clear that success, ultimately, must be judged in boosting the wild population. If the descendants of these birds make the return to the wild then we will know we have succeeded. But for now, we should celebrate a very significant milestone."