Loss of rainforest threatens the Rhinoceros Hornbill (picture: C.Artuso)

Conservation group Birdlife International said 323 species out of total of 2,700 were facing extinction, with Indonesia home to about a third of them.

China had the second largest number of threatened birds in the region with 78, followed by India with 73 and Philippines with 69.

The study, published to coincide with United Nations World Environment Day, showed a dramatic rise in the same figures over the last 20 years - in 1998, only 51 bird species were under threat.

Some birds are very vulnerable as they are confined to single islands (picture: J Riley)

Birdlife International has also said it had "conservation concern" for 25% of all Asian bird species.

"It's a shocking figure," Michael Szabo, the organisation's communications manager told BBC News Online. "[We're] gravely concerned."

Birdlife also said 41 species were "critically endangered", and of those, 11 could already be extinct.

Humans to blame

The organisation - which has published its findings in a book entitled Threatened Birds of Asia: The Birdlife International Red Data Book - said human activity was 100% to blame in all cases.

There are less than 650 Philippine Eagles (picture:Chris Rose/Rare Bird Club)

"Obviously, population pressure and economic growth are linked [to the figures]," said Mr Szabo. "There's very high pressure on natural resources."

Logging is the biggest threat, affecting 50% of all endangered species, followed by arable farming, which affects 30%, and shifting agriculture at 20%.

Mr Szabo said some birds were dependent on a specific site. "So if anything happens to that forest - if it was logged or burnt - it would make that bird very vulnerable," he said.

He cited the Caerulean Paradise-Flycatcher, which was confined to a patch of forest on Indonesia's Sangihe island.

The book was launched in Tokyo. "Birds recognise no national borders and therefore concerted action and co-operation between countries is critical," Japan's Princess Takamado said during the launch.

Hope

Birdlife International urged measures such as extending protected areas, new legislation and greater education.

Water birds are especially threatened (picture: J Hornbuckle)

"Governments, companies and conservation groups can turn the tide but we must act urgently," said Mr Szabo.

The organisation said many large water birds were already very close to extinction.

Planned coastal reclamation in east China and the Korean peninsula also threatened to disrupt the migratory routes of threatened species, it added.

The study, sponsored by Japan's environment ministry and involving local nature groups, was the most comprehensive to date, covering 23 Asian countries, the organisation said.