The corpse is sent to the burial site among mountains
Scent of juniper invites clusters of vultures to hover above the site. Then a 'daodeng', the man who is in charge of the burial process, begins to slice the body.
Vultures swoop down and peck at the flesh and the bones scattered around. Any remains left by these huge birds would tie the spirits to this life, so they must be collected up while monks are invited to patter the dead at the same time. After they are cremated, the ashes are scattered into air. At this time the deceased completes the move on to nirvana.
source : http://muzich.blogspot.com/2009/09/tibetan-sky-burial.html