A ruddy shelduck and a flock of barhead geese fly over a wetland in Nyima County, southwest China's Tibet Autonomous Region, Sept. 19, 2017. Changtang National Nature Reserve is a wildlife paradise and home to a variety of wildlife species such as Tibetan antelopes, wild yaks, Tibetan wild donkeys and black-necked cranes. (Xinhua/Zhang Rufeng)

Two Tibetan wild donkeys gallop on a pasture in Nyima County, southwest China's Tibet Autonomous Region, Sept. 19, 2017. Changtang National Nature Reserve is a wildlife paradise and home to a variety of wildlife species such as Tibetan antelopes, wild yaks, Tibetan wild donkeys and black-necked cranes. (Xinhua/Zhang Rufeng)

Tibetan antelopes gallop on a pasture in Nyima County, southwest China's Tibet Autonomous Region, Sept. 19, 2017. Changtang National Nature Reserve is a wildlife paradise and home to a variety of wildlife species such as Tibetan antelopes, wild yaks, Tibetan wild donkeys and black-necked cranes. (Xinhua/Zhang Rufeng)

Black-necked cranes are seen on a wetland in Nyima County, southwest China's Tibet Autonomous Region, Sept. 19, 2017. Changtang National Nature Reserve is a wildlife paradise and home to a variety of wildlife species such as Tibetan antelopes, wild yaks, Tibetan wild donkeys and black-necked cranes. (Xinhua/Zhang Rufeng)