As winter falls, over 10,000 pochards have flocked to a wetland on the Yellow River in Sanmenxia, central China's Henan Province. The migratory birds usually come from Xinjiang Uygur Autonomous Region. Standing on the river bank, people watch them on the surface of the water, chasing and playing with each other. In addition to pochards, thousands of white swans from Siberia also spend the winter in the city, from mid-October to March every year. The city witnesses a rise in the number of swans during the annual migration season. This has earned it the nickname "city of swans." Sanmenxia has become a bird-watchers' dream.