On the outskirts of Lhasa, Tibetan mourners whispered prayers, while hungry brooding vultures circled overhead.Cawing."This is our sky funeral. We let the vultures eat the bodies of dead Tibetans," a mourner said as we sat on rocky dirt among other Tibetan mourners at the beginning of the somber rites. "I personally think it is too gruesome. But this is our Buddhist tradition."Cremations and burials are difficult to perform. Firewood is scarce t…