By Daniel Lak in Delhi

In India and other developing countries where standards of hygiene are low, vultures help keep the environment clean by eating up rotting animal carcasses.

Millions of cows die everyday in India, and very few people eat beef because of their Hindu faith.

Vultures are therefore crucial.

That is why scientists and ornithologists around the world are alarmed that India's vulture population seems to be dying off.

Some experts estimate that there has been a 98% drop in the population of the two most common species of vultures in India, based on surveys in one of the country's leading game preserves.

They believe it is time for action.

Vulture 'restaurants'

S M Satheesan of the World Wide Fund for nature is proposing a chain of "vulture restaurants" to keep the soaring scavengers from disappearing altogether.

"It would be an enclosure, open at the top with places for the birds to perch," he says.

"Clean carcasses, no poison, no pesticides, clean water and most importantly, a safe environment would be available."

Vultures are the main cause of aircraft accidents because they are big and slow get easily sucked into passing jet engines.

Dr Satheesan has studied the vulture population around Delhi airport for years and says restaurants placed strategically might also save human lives by luring the birds from around the runway.

Others disagree.

Dr Asad Rahmani of the Bombay natural history society says vultures aren't dying of starvation.

No food shortage

According, to him, the problem is not a shortage of food.

"There are many carcasses lying around all over north India," he points out.

"There are two probable causes for all the vulture deaths: pesticides and poisons, or disease. We think we now which is responsible."

Keo Ladeo national park, south of Delhi, was once home to thousands of vultures.

Local guide Ratan Singh has watched the population plunge to less than ten in the past three years.

Now he usually just shows his charges empty nests in the park's towering teak trees.

"There used to be three, four thousand vultures in this park. They were everywhere. Now there is only one flying past every few weeks. And the nests are empty," he says.

Disease

Work by ornithologist Vibhu Prakash has lead him to rule out pesticide poisoning, food shortages and predators - leaving only disease.

"The birds sit in the trees and those with disease slump their necks. Healthy birds sit up straight. Especially in the hot weather, you can tell which ones are sick. I think the whole species is infected," he says.

Vibhu Prakash says it's not too far fetched to remind people that AIDS and mad cow disease both began as sicknesses that affected animals.

Tourists may not come from abroad to Keo Ladeo to see vultures, but park naturalists are explaining the scavenger birds� plight to visitors in the hope that international attention will save one of India's most important bird species.