Black-necked cranes and other migrant birds are seen at the Caohai National Nature Reserve in Weining Yi, Hui and Miao Autonomous County, southwest China's Guizhou Province, Feb. 22, 2022. 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. (Photo by He Huan/Xinhua)

Black-necked cranes and other migrant birds are seen at the Caohai National Nature Reserve in Weining Yi, Hui and Miao Autonomous County, southwest China's Guizhou Province, Feb. 22, 2022. 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. (Photo by He Huan/Xinhua)

Black-necked cranes and other migrant birds are seen at the Caohai National Nature Reserve in Weining Yi, Hui and Miao Autonomous County, southwest China's Guizhou Province, Feb. 22, 2022. 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. (Photo by He Huan/Xinhua)

Black-necked cranes and other migrant birds are seen at the Caohai National Nature Reserve in Weining Yi, Hui and Miao Autonomous County, southwest China's Guizhou Province, Feb. 22, 2022. 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. (Photo by He Huan/Xinhua)

Aerial photo shows black-necked cranes and other migrant birds at the Caohai National Nature Reserve in Weining Yi, Hui and Miao Autonomous County, southwest China's Guizhou Province, Feb. 22, 2022. 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. (Photo by He Huan/Xinhua)

Black-necked cranes and other migrant birds are seen at the Caohai National Nature Reserve in Weining Yi, Hui and Miao Autonomous County, southwest China's Guizhou Province, Feb. 22, 2022. 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. (Photo by He Huan/Xinhua)

Migrant birds are seen flying in the sky at the Caohai National Nature Reserve in Weining Yi, Hui and Miao Autonomous County, southwest China's Guizhou Province, Feb. 22, 2022. 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. (Photo by He Huan/Xinhua)

Black-necked cranes and other migrant birds are seen at the Caohai National Nature Reserve in Weining Yi, Hui and Miao Autonomous County, southwest China's Guizhou Province, Feb. 22, 2022. 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. (Photo by He Huan/Xinhua)

Black-necked cranes and other migrant birds are seen at the Caohai National Nature Reserve in Weining Yi, Hui and Miao Autonomous County, southwest China's Guizhou Province, Feb. 22, 2022. 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. (Photo by He Huan/Xinhua)

来源：Xinhua