Swans rest in the anjiangkou wetland of Xigu district in Lanzhou, Gansu province. [Photo provided to Lanzhou.gogansu.com]

After Spring Festival, the weather in the anjiangkou wetland of Xigu district in Lanzhou, Northwest China's Gansu province gradually warms up. 

The whooper swans, which have accompanied people throughout the winter, are preparing to migrate north.