A black-necked crane looks after its chicks after they hatched in the Qiangtang nature reserve, southwest China's Tibet Autonomous Region, June 24, 2017. Flocks of black-necked cranes fly here to breed as the environment of reserve has been improved in recent years. (Xinhua/Purbu Zhaxi)

A black-necked crane looks after its chicks after they hatched in the Qiangtang nature reserve, southwest China's Tibet Autonomous Region, June 23, 2017. Flocks of black-necked cranes fly here to breed as the environment of reserve has been improved in recent years. (Xinhua/Purbu Zhaxi)

A black-necked crane looks after its chick after it hatched in the Qiangtang nature reserve, southwest China's Tibet Autonomous Region, June 24, 2017. Flocks of black-necked cranes fly here to breed as the environment of reserve has been improved in recent years. (Xinhua/Purbu Zhaxi)

A black-necked crane looks after its chicks after they hatched in the Qiangtang nature reserve, southwest China's Tibet Autonomous Region, June 23, 2017. Flocks of black-necked cranes fly here to breed as the environment of reserve has been improved in recent years. (Xinhua/Chogo)

Black-necked cranes look after their chick after it hatched in the Qiangtang nature reserve, southwest China's Tibet Autonomous Region, June 23, 2017. Flocks of black-necked cranes fly here to breed as the environment of reserve has been improved in recent years. (Xinhua/Chogo)

A black-necked crane looks after its chick after it hatched in the Qiangtang nature reserve, southwest China's Tibet Autonomous Region, June 23, 2017. Flocks of black-necked cranes fly here to breed as the environment of reserve has been improved in recent years. (Xinhua/Chogo)