Aerial photo taken on Nov. 20, 2019 shows migratory birds at Guanting Reservoir National Wetland Park in Huailai County, north China's Hebei Province. In recent years, Huailai County has stepped up ecological construction and effectively improved the ecological environment. Guanting reservoir has become a transit place and habitat for the annual migration of a variety of migratory birds. (Xinhua/Yang Shiyao)