In late March, Wolong Lake in Shenyang, northeast China, welcomes its annual migratory bird season. Tens of thousands of birds sweep across the lake, forming a stunning "bird wave."

A key lake in the Liaohe River basin, it becomes a vital stopover each spring for hundreds of thousands of migratory birds, including Siberian cranes, oriental storks, wild geese and grey herons, as they rest and refuel for their journey.■