In this aerial photo taken on Nov. 11, 2020, a flock of migratory birds fly over the West Dongting Lake in Changde, central China's Hunan Province. The West Dongting Lake, along with its biologically rich wetlands, has been a thoroughfare for migratory birds. About 20,000 migratory birds have arrived at West Dongting Lake so far this year. (Xinhua/Chen Sihan)