Swan Lake Wetland Park, along the Yellow River below the Sanmenxia Dam, hosts one of the largest concentrations of migrating Siberian whooper swans in China between October and February. The birds — up to 60,000 or more in peak years — arrive from breeding grounds in Siberia and Inner Mongolia and overwinter here where the dam's regulated water keeps sections of the river open and food-rich. Access to the wetland is free, and the swans are typically close enough to photograph without a telephoto lens; on good days the entire surface of some sections of the river appears white with birds.
The best viewing is in the early morning when the birds are most active and the light is at its softest. The main observation area is a short taxi ride from the city centre. November to January is the peak period; by late February the birds begin moving north again. The surrounding wetland also hosts other wintering waterbirds including egrets, herons, and various ducks, but the swans dominate. Bring warm clothing — the Yellow River valley in winter is cold and windy.