Migratory birds seen in NW China's Gansu as weather warms up

White swans fly on the Xiaosugan lake wetland in Kazak Autonomous County of Aksay, northwest China's Gansu Province, April 5, 2019. Migratory birds like white swans, black-necked cranes and bar-headed geese are seen here as the weather warms up. (Xinhua/Chen Bin)