The numbers of both species have plunged in Nepal and India and scientists say the decline is largely due to farmers dosing their cattle with diclofenac, a drug used to treat inflammation, poisoning the scavenging birds.

The plan is to capture at least 10 breeding pairs of vultures for each of the critically endangered species and keep them initially in two aviaries at Kasara in Chitwan National Park, said Dev Ghimire, an official with Bird Conservation Nepal.

The park, located 80 km (50 miles) southwest of Kathmandu, is popular for its rare Asian rhinoceroses.

"This is just a beginning and more pairs will be subsequently trapped and released," Ghimire said. "It is a very important project and needs long-term commitment."

Conservationists estimate the number of vultures in Nepal to have dropped to about 500 nesting pairs from 50,000 in 1990, primarily from eating dead cattle treated with diclofenac.

Bird Conservation Nepal has already set up a separate feeding centre west of Chitwan for white-rumped and slender-billed vultures offering them chemical-free carcasses.

The number of vultures at the centre has risen since the complex was opened last year.

Birds for the breeding programme are to be caught in the wild from March during the breeding season when it is easy to trap them.

"We can use the techniques and expertise applied by conservationists in India which also has vulture breeding centres," he said.