Migrant birds fly over the Caohai National Nature Reserve in Weining Yi, Hui and Miao Autonomous County, Bijie, southwest China's Guizhou Province, Feb. 1, 2021. Caohai was listed as a national nature reserve in 1992 and is an important wintering ground and migration transfer station for birds such as black-necked cranes, grey cranes and spotted geese. In recent years, Guizhou Province has vigorously promoted comprehensive measures and wetland restoration in Caohai National Nature Reserve, with more than 100,000 birds coming to overwinter every year.[Photo/Xinhua]