As temperatures dropped, 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.

Overlooking the Taipingyao Reservoir, the deep blue water was dotted with white whooper swans. Photographers gathered to take candids of the swans preening and flying in pairs.

In the past, there were some ecological problems in the upper reaches of the Sanggan River, such as the decrease of the groundwater level, the attenuation of river runoff and the degradation of vegetation.

With the implementation of the ecological water diversion project and the vigorous promotion of ecological environment control, the ecological environment of the river basin has been significantly improved, and more and more migratory birds are choosing to live here for the winter.