Tens of thousands of migratory birds have made a stopover at the banks of the Sanggan River in Shuozhou City, northern China's Shanxi Province. They are taking a rest at the river on their northbound journey as temperatures rise in spring. In the coming weeks, more migratory birds are expected to arrive. Experts say in spring and summer, northern regions offer longer daylight hours, which provide more time for the birds to find food and care for their young.