Construction is scheduled to begin as soon as April, said Dinshaw Rus Mehta, chairman of the Bombay Parsi Punchayet. If all goes as planned, he said, vultures may again consume the Parsi dead by January 2014.
"Without the vultures, more and more Parsis are choosing to be cremated," Mehta said. "I have to bring back the vultures so the system is working again, especially during the monsoon."
The plan is the result of six years of negotiations between Parsi leaders and the Indian government to revive a centuries-old practice that seeks to protect the ancient elements - air, earth, fire and water - from being polluted by either burial or cremation. And along the way, both sides hope the effort will contribute to the revival of two species of vulture that are nearing extinction. The government would provide the initial population of birds.
The cost of building the aviaries and maintaining the vultures is estimated at $5 million spread over 15 years, much less expensive than it would have been without the ready supply of food.
"Most vulture aviaries have to spend huge sums to buy meat, but for us that's free because the vultures will be feeding on human bodies - on us," Mehta said.
Like the vultures on which they once relied, Parsis are disappearing. Their religion, Zoroastrianism, once dominated Iran but was largely displaced by Islam. In the 10th century, a large group of Zoroastrians fled persecution in Iran and settled in India. Fewer than 70,000 remain, most of them concentrated in Mumbai, formerly known as Bombay, where they collectively own prime real estate that was purchased centuries ago.
Among the most valuable of these holdings are 54 acres of trees and winding pathways on Malabar Hill, one of Mumbai's most exclusive neighbourhoods. Tucked into these acres are three Towers of Silence where Parsis have for centuries disposed of their dead.
The stone towers are open-air auditoriums containing three concentric rings of marble slabs - an outer ring for dead men, middle ring for deceased women and inner ring for dead children. For centuries, bodies left on the slabs were consumed within hours by neighbourhood vultures, with the bones left in a central catchment to leach into the soil.
Modernity has impinged on this ancient practice in many ways. That includes the construction of nearby skyscrapers where non-Parsis could watch the grisly scenes unfold. But by far the greatest threat has been the ecological disaster visited in recent years on vultures.
India once had as many as 400 million vultures, a vast population that thrived because the nation has one of the largest livestock populations in the world but forbids cattle slaughter. When cows died, they were immediately set upon by flocks of vultures that left behind skin for leather merchants and bones for bone collectors. As recently as the 1980s, even the smallest villages often had thousands of vulture residents.
But then came diclofenac, a common painkiller widely used in hospitals to lessen the pain of the dying. Marketed under names like Voltaren, it is similar to the medicines found in Advil and Aleve; in 1993 its use in India was approved in cattle. Soon after, vultures began dying in huge numbers because the drug causes them to suffer irreversible kidney failure.
Diclofenac's veterinarian use has since been banned, which may finally be having an effect. A recent study found that for the first time since the drug's introduction, India's vulture population did not decline over the past year.
Still, the numbers for three species have shrunk to only a few thousand, a tiny fraction of their former levels. With so few vultures left, the Parsi community set up mirrors around the Towers of Silence to create something akin to solar ovens to accelerate decomposition. But the mirrors are ineffective during monsoon months. So an increasing number of Parsis are opting for cremation, a practice many Parsi priests believe is an abomination since fire is sacred and corpses are unclean.
Desperate to maintain one of their most important rituals, Parsi leaders have created detailed plans to build the aviaries near the Towers of Silence, each housing 76 vultures. Parsi leaders say they are waiting for formal approval from community members, doctors and priests before beginning construction, approvals they expect to receive over the next several weeks.
But Homi B. Dhalla, president of the World Zarathushti Cultural Foundation, has promised to fight the plans. He helped to develop the tower solar collectors and said they were working well. And he is worried that once the government provides vultures for Parsi aviaries, bureaucrats will try to seize the land.
"Why endanger our property?" Dhalla asked. "Who is going to fight the government?"
Another concern is whether Parsis can be persuaded to stop using diclofenac. Nearly all of the roughly 800 bodies brought annually to the towers come from two Parsi hospitals, and doctors and family would have to certify that the deceased had not been given diclofenac in the three days before death. There is no simple test to detect the drug, and if vultures in the aviaries die from diclofenac poisoning after eating Parsi corpses the government has promised to end the effort.
Parsi medical leaders were cautious in their comments about the vulture program.
"As a hospital," said Dr. S.K. Dhingra, superintendent of B.D. Petit Parsee General Hospital, "we cannot tell our patients, 'You can do this, or you can do that."'
Khurshed Dastoor, one of five Parsi high priests, said that he was not sure members would adhere to a diclofenac ban.
"For 10 years, I have been trying to educate the community to turn off their cellphones before they go inside our most sacred fire temples, and I have failed," he said. "And now we think the community will give up diclofenac in a couple of months?"
Other Parsi leaders, however, said they were pushing ahead because of the importance of restoring the tradition.
"We must hope for the best," Mehta said.
(Sruthi Gottipati contributed reporting.)