A flock of black-necked cranes are pictured at the Caohai National Nature Reserve, a popular destination among migratory birds, in Weining Yi-Hui-Miao Autonomous County, Bijie, southwest China's Guizhou Province, Nov. 16, 2020. (Photos: Xinhua)

A flock of black-necked cranes are pictured at the Caohai National Nature Reserve, a popular destination among migratory birds, in Weining Yi-Hui-Miao Autonomous County, Bijie, southwest China's Guizhou Province, Nov. 16, 2020.

A flock of black-necked cranes hover over the Caohai National Nature Reserve, a popular destination among migratory birds, in Weining Yi-Hui-Miao Autonomous County, Bijie, southwest China's Guizhou Province, Nov. 16, 2020.

A flock of black-necked cranes hover over the Caohai National Nature Reserve, a popular destination among migratory birds, in Weining Yi-Hui-Miao Autonomous County, Bijie, southwest China's Guizhou Province, Nov. 16, 2020.

A flock of black-necked cranes hover over the Caohai National Nature Reserve, a popular destination among migratory birds, in Weining Yi-Hui-Miao Autonomous County, Bijie, southwest China's Guizhou Province, Nov. 16, 2020.

A flock of black-necked cranes hover over the Caohai National Nature Reserve, a popular destination among migratory birds, in Weining Yi-Hui-Miao Autonomous County, Bijie, southwest China's Guizhou Province, Nov. 16, 2020.

Two black-necked cranes hover over the Caohai National Nature Reserve, a popular destination among migratory birds, in Weining Yi-Hui-Miao Autonomous County, Bijie, southwest China's Guizhou Province, Nov. 16, 2020.

A flock of black-necked cranes are pictured at the Caohai National Nature Reserve, a popular destination among migratory birds, in Weining Yi-Hui-Miao Autonomous County, Bijie, southwest China's Guizhou Province, Nov. 16, 2020.