Swans fly in the Sanwan wetland on the Yellow River in Pinglu County of Yuncheng, north China's Shanxi Province, Nov. 8, 2018. More than 1,000 swans have flown from Siberia to the Sanwan wetland to spend the winter. The number of migratory swans here is expected to exceed 5,000 in late November. (Xinhua/Liu Wenli)