Photo taken on Feb. 21, 2019 shows black-necked cranes at Caohai National Nature Reserve in Weining County, southwest China's Guizhou Province. Caohai National Nature Reserve is one of the main habitats for black-necked cranes to winter from late October to the end of March of next year. (Xinhua/Hu Panxue)

　　Photo taken on Feb. 21, 2019 shows black-necked cranes flying over Caohai National Nature Reserve in Weining County, southwest China's Guizhou Province. Caohai National Nature Reserve is one of the main habitats for black-necked cranes to winter from late October to the end of March of next year. (Xinhua/Hu Panxue)

　　Photo taken on Feb. 21, 2019 shows black-necked cranes flying over Caohai National Nature Reserve in Weining County, southwest China's Guizhou Province. Caohai National Nature Reserve is one of the main habitats for black-necked cranes to winter from late October to the end of March of next year. (Xinhua/Hu Panxue)

　　Photo taken on Feb. 21, 2019 shows black-necked cranes skimming the surface of water at Caohai National Nature Reserve in Weining County, southwest China's Guizhou Province. Caohai National Nature Reserve is one of the main habitats for black-necked cranes to winter from late October to the end of March of next year. (Xinhua/Yang Ying)

　　Photo taken on Feb. 21, 2019 shows black-necked cranes at Caohai National Nature Reserve in Weining County, southwest China's Guizhou Province. Caohai National Nature Reserve is one of the main habitats for black-necked cranes to winter from late October to the end of March of next year. (Xinhua/Yang Ying)

　　Photo taken on Feb. 21, 2019 shows black-necked cranes at Caohai National Nature Reserve in Weining County, southwest China's Guizhou Province. Caohai National Nature Reserve is one of the main habitats for black-necked cranes to winter from late October to the end of March of next year. (Xinhua/Yang Ying)

　　Photo taken on Feb. 21, 2019 shows black-necked cranes at Caohai National Nature Reserve in Weining County, southwest China's Guizhou Province. Caohai National Nature Reserve is one of the main habitats for black-necked cranes to winter from late October to the end of March of next year. (Xinhua/Han Xianpu)

　　Photo taken on Feb. 21, 2019 shows black-necked cranes at Caohai National Nature Reserve in Weining County, southwest China's Guizhou Province. Caohai National Nature Reserve is one of the main habitats for black-necked cranes to winter from late October to the end of March of next year. (Xinhua/He Huan)

　　Photo taken on Feb. 21, 2019 shows black-necked cranes at Caohai National Nature Reserve in Weining County, southwest China's Guizhou Province. Caohai National Nature Reserve is one of the main habitats for black-necked cranes to winter from late October to the end of March of next year. (Xinhua/Luo Dafu)