Aerial photo taken on Jan. 9, 2020 shows whooper swans at the national nature reserve for whooper swans in Rongcheng City, east China's Shandong Province. With unique geographical location and comprehensive ecological protection of wetlands, Rongcheng provides favorable natural conditions for thousands of whooper swans to spend winter. The nature reserve for whooper swans here was established in 1985 and promoted to the state level in 2007. (Xinhua/Hou Dongtao)