Recently, a large number of migratory birds have arrived at the wetlands of the Yalu River estuary in Dandong City, Liaoning Province. Bird lovers flock to Dandong City to capture photographs of these migratory birds, and the Yalu River estuary becomes the most-welcomed spot as they can observe the magnificent view of “bird waves”. As the setting sun casts a golden glow, thousands of birds fly in unison. From afar, they look like waves in the sky, creating a splendid ecological view.