But this bird, along with 17 others of the same species, was intercepted by Russian customs officers. All were released back into the wild in the Altai region of southern Siberia on Monday.

"All of these birds have had a tough time," said Sergei Ganusevich, director of the Moscow Centre for the Protection of Wild Animals, who flew to the Altai region to watch the falcons go free.

"All the falcons were caught illegally in (the Siberian region of) Khakassia and were being prepared for smuggling to Arab countries, where hunting with falcons is a favourite local pastime," he said.

He said five of the birds were intercepted in Moscow a month ago. A Syrian smuggler was try to ship them out in a sports bag.

"As a rule, the smugglers do not care about the state of their goods. They can starve them, and some of the birds just suffocate in cramped boxes," said Ganusevich.

Saker falcons -- which can have a wing span of up to 130 cm (more than four feet) -- are found in a wide arc from eastern Europe to western China. Numbers have been in decline because of a loss of habitat and poaching.

According to the World Conservation Union, a Switzerland-based group, the world population was estimated in 2003 at a maximum of 4,400 pairs.

The Altai region was chosen to release the birds because it is one of the species' natural habitats and poaching is less widespread there than in other parts of Russia.

The falcons were brought in special crates by air from Moscow, then driven into the forest about 70 km (44 miles) outside the regional capital, Barnaul. They were then set free one by one.

"The return of every bird into the wild is a unique process and for us it is also a great joy," said Viktor Plotnikov, director of the Barnaul falcon sanctuary.