India's powerful Parsi community—descendants of Persian refugees from an all-conquering Islam—have well-known and distinctive death rites: instead of burying or cremating their corpses, devout Zoroastrians leave the bodies out for vultures to devour. Now that 2,000-year-old ritual may itself be dying out. In recent years, India's white-backed vulture population has begun to drop, a victim of what some ornithologists contend is a virus sweeping across South Asia and threatening the species with extinction. To protect their way of death—and to save the birds of prey—Parsis in Bombay are making plans to set up an enormous aviary around the towers of silence where the rituals take place, to breed enough vultures to cope with the average of three human corpses that are placed there daily. The move has drawn criticism from reform-minded Parsis who argue that it's time to move on to more modern methods for disposing of the dead. But the obvious alternatives—cremation and burial—are anathema to orthodox leaders of a religion that treats fire, earth and water as symbols of divine purity. We have to consider what is doctrinally right for the religion, says Khojeste Mistree, an Oxford-educated Zoroastrian scholar. We cannot ignore the religious aspect of the mode of disposal.Where India's Parsis have established new communities—in North America, Britain, Australia, New Zealand and elsewhere—the faithful are buried within slabs of stone so that no soil will touch the corpse and be defiled. It may seem perfectly normal for some people to bury a body in the ground, says Mistree. To me it is repulsive that worms are eating a body for as long as 60 years. At the towers it takes a flock of vultures only two hours to dispose of the dead. That was when there were vultures. Today there are mostly only kites, crows and the sun's rays, and the process can take days, even weeks. The towers—an English misnomer for the small, open-air amphitheaters that Zoroastrians call dakhma—are hidden amid 20 hectares of dense jungle on Malabar Hill, now Bombay's most valuable piece of real estate. Parsis call it the city's lungs, the last great swath of green in a smoggy metropolis of 13 million. As evidence both of Parsi influence and official respect for the religion, Indian authorities ban aircraft from overflying the area. Unfortunately, the vultures aren't overflying either. The north Indian plain, from Bengal in the east to Punjab in the west, was once home to tens of thousands of the white-backed birds. They were everywhere—in fields, on the edge of towns, perched in trees and on telegraph poles. Today a casual visitor would be lucky to see even one. The situation is extremely serious, says ornithologist Vibhu Prakash, who has been monitoring the vultures since 1986. Even in protected areas there has been a complete wipeout. From his station at the Bharatpur bird sanctuary in Rajasthan, he recorded 350 nesting pairs in 1987. Ten years later there were 25 pairs. This year he found none. What's killing the birds? Experts first suspected pesticides, toxic substances and modern farming methods. But ornithologists now point to an unidentified virus that they believe may have originated in Southeast Asia, where vultures disappeared 50 years ago. It causes what is known as drooping neck syndrome, which is accompanied by stomach cramps, dehydration and enteritis. The birds normally hang their necks during the hottest part of the day. But once infected they droop all the time. The birds typically die six months after contracting the disease.Parsi leaders are battling against time. After overcoming doubters within Bombay's 76,000-member community, the religion's trustees in the city unanimously agreed last month to seek government approval for the vulture aviary and breeding program. The Parsis have already set aside funds for it. There is an element of apprehension, says trustee Dinshaw Mehta, referring to the cost of the project and fears that it might fail. But what we are doing is doctrinally sound. It will bring credit to India. We will be protecting a threatened species. It will not cost the government a single rupee. The initial plan involves building a 15-m-high aviary over about half a hectare that will include one of the three working dakhma at an estimated cost of $220,000; thereafter the aviary is expected to require $44,000 in upkeep every year. It will be stocked with 50 pairs of juvenile vultures—birds that are not yet accustomed to scavenging for food and that would adapt easily to the relatively confined space. The birds would reach maturity in seven years and then be ready to mate. Eventually, planners expect the site to include up to three aviaries as well as additional breeding centers. The goal is to add fresh genes to the original flock and then release vultures into the wild across north India. In September a group of Indian and foreign ornithologists met in New Delhi to draw up an action plan to save South Asia's vultures. The Parsi aviary is a critical part of it. If we can contribute to India's ecological well-being by establishing the country's first captive vulture breeding center, says Mehta, we will be proud citizens and happy Parsis. It's a win-win situation.