More than 1,500 whooper swans flew to the Sanggan River in Shuozhou City, north China's Shanxi Province, for the winter, exceeding the local historical statistics. The swans were seen preening and flying in pairs along the river. Decrease of the groundwater level in the upper reaches of the Sanggan River caused the easing of river runoff and the degradation of vegetation. The ecological water diversion project has improved the environment, causing more migratory birds to choose to spend the winter here.