Sky burials are a funerary practice in the Chinese provinces of Tibet, Qinghai, and Inner Mongolia and in Mongolia. The majority of Tibetans and many Mongolians adhere to Vajrayana Buddhism, which teaches the transmigration of spirits.This means they do not see a need to preserve the body, as it is now an empty vessel, so they dispose of it through a sky burial.
In the days leading up to the ceremony monks - known as lamas - may chant mantra around the body and burn juniper incense.The body is then chopped into pieces by either monks - known as lamas - or more commonly, by rogyapas (body-breakers). Eyewitness accounts suggest the body-breakers do the grim task in high-spirits - according to Buddhist teaching, this makes it easier for the soul of the deceased to move on. It is difficult to ascertain the exact process as Tibetans strongly object to visits by the merely curious, but it is thought the whole body is given to the vultures. Some stories suggest the body parts are left in the Tower of Silence for a year, exposed to the elements and birds - men and women are placed in different sections. Then when only the bones are left, the pieces are broken up with mallets, ground with tsampa (barley flour with tea and yak butter, or milk), and given to the crows and hawks that have waited for the vultures to depart.The function of the sky burial is simply to dispose of the remains in as generous a way as possible - this donation of human flesh to the vultures is considered virtuous because it saves the lives of small animals that the vultures might otherwise capture for food.
and Sky Burial Remnants here