A swan flies over Shijiu Lake in Nanjing, east China's Jiangsu Province, Nov. 18, 2020. (Xinhua/Ji Chunpeng)

Swans fly over Shijiu Lake in Nanjing, east China's Jiangsu Province, Nov. 18, 2020. (Xinhua/Ji Chunpeng)

Swans fly over Shijiu Lake in Nanjing, east China's Jiangsu Province, Nov. 18, 2020. (Xinhua/Li Bo)

Swans are seen on Shijiu Lake in Nanjing, east China's Jiangsu Province, Nov. 18, 2020. (Xinhua/Li Bo)

Swans are seen on Shijiu Lake in Nanjing, east China's Jiangsu Province, Nov. 18, 2020. (Xinhua/Ji Chunpeng)