A flock of cranes fly over the National Nature Reserve of Black-necked Cranes in Huize County of Qujing City, southwest China's Yunnan Province, Nov. 19, 2020. Large numbers of migratory birds including black-necked cranes and grey cranes flied here for wintering. (Photos: Xinhua)

A flock of cranes fly over the National Nature Reserve of Black-necked Cranes in Huize County of Qujing City, southwest China's Yunnan Province, Nov. 18, 2020.

Cranes fly over the National Nature Reserve of Black-necked Cranes in Huize County of Qujing City, southwest China's Yunnan Province, Nov. 19, 2020.

flock of grey cranes are seen in the National Nature Reserve of Black-necked Cranes in Huize County of Qujing City, southwest China's Yunnan Province, Nov. 19, 2020.