Here is a detailed explanation regarding the premise of your request.

The Short Answer

There is no historical evidence to support the claim that Zoroastrian communities in medieval Persia deliberately bred "corpse-detection vultures."

While Zoroastrians did (and some still do) rely heavily on vultures for their funerary practices, the idea that they engaged in the captive breeding or genetic selection of these birds for specific traits is a modern misconception or a fictional fabrication. The relationship was ecological and opportunistic, not agricultural or scientific.

To understand why this specific claim is inaccurate—and to understand the actual, fascinating history of Zoroastrian funerary rites—we must look at the religious, ecological, and historical context of the Dakhma.

1. The Theological Basis: Purity and Pollution

In Zoroastrianism, the ancient pre-Islamic religion of Persia, the elements of nature (earth, fire, and water) are considered sacred and pure. Conversely, a human corpse (nasu) is viewed as highly polluting. It is believed that as soon as the soul leaves the body, a "corpse demon" (Druj-i-Nasu) rushes in to contaminate it.

Therefore, traditional burial (which pollutes the earth) and cremation (which pollutes the fire) were strictly forbidden.

The Solution: Dokhmenashini (Sky Burial) The solution was the exposure of the dead. Bodies were placed atop raised, circular stone structures called Dakhmas (often translated as "Towers of Silence"). Here, the bodies were exposed to the sun and to scavenging birds. This method was seen as the most hygienic and ecologically sound way to dispose of the dead without defiling the sacred elements.

2. The Role of Vultures in Medieval Persia

Vultures were essential to this process, but they were wild, not domesticated.

• Natural Scavengers: Persia (modern-day Iran) historically had thriving populations of Griffon vultures and Bearded vultures. These birds are naturally evolved "corpse detectors." They have incredible eyesight and can spot a carcass from miles away. There was no need to breed them for this trait; nature had already perfected it.
• The Symbiotic Relationship: Zoroastrian communities built their Towers of Silence on hilltops or mountains, far from population centers but within the natural habitat of these birds. The vultures learned that these structures provided a reliable food source. It was a localized ecosystem: the humans provided the food, and the vultures provided the disposal service.
• Lack of Domestication: Vultures are notoriously difficult to breed in captivity, even with modern technology. In the medieval period, the resources required to capture, house, and breed large raptors would have been astronomical and unnecessary, given that wild populations were abundant.

3. Origins of the Misconception

If this didn't happen, where does the idea come from?

• Misinterpreting "Care": Historical records indicate that priests or guardians of the Dakhmas might have monitored vulture populations or worried when bird numbers dropped (as this slowed the decomposition process). This concern for the birds' presence might be misinterpreted by modern readers as "husbandry."
• Modern Vulture Crises: In recent decades (particularly among the Parsi community in India), vulture populations have collapsed due to poisoning from the veterinary drug diclofenac. This has led to a real, modern crisis where bodies in the Towers of Silence are not decomposing. In response, there have been modern discussions about aviaries and captive breeding programs to save the vultures. It is possible that someone has conflated these 21st-century conservation proposals with medieval history.
• Fiction and Folklore: The idea of "breeding corpse-detection birds" sounds like a plot point from dark fantasy or Gothic horror. It is possible this specific phrasing comes from a novel, game, or speculative fiction setting rather than an archaeological text.

4. The Actual Process in Medieval Persia

Instead of breeding birds, the actual medieval practice involved architectural and ritual precision:

1. The Procession: The body was carried by professional corpse-bearers (Nassalars) who were ritually secluded from the rest of society due to their contact with the dead.
2. The Tower: The Dakhma was a sophisticated filtration system. It was a circular pit paved with stone. Bodies were arranged in concentric circles (men outer, women middle, children inner).
3. The Stripping of Flesh: Wild vultures would strip the bones of flesh in a matter of hours. This rapid defleshing was considered a kindness, releasing the soul and preventing the prolonged rot associated with the "corpse demon."
4. The Sun and the Pit: Once the bones were stripped, the intense Persian sun would bleach and dry them. Eventually, the bones were swept into a central ossuary pit (bhandar) where they crumbled into dust, aided by lime and rain, eventually filtering through charcoal and sand before returning to the earth in a purified state.

Summary

The Zoroastrians of medieval Persia were masters of eco-theology, utilizing the natural food chain to solve a spiritual dilemma. They relied on the natural instincts of wild vultures, but there is no historical record of them breeding these birds. The vultures were considered useful agents of purification, but they remained wild creatures of the sky, not livestock of the community.