Starlings during the autumn migration between Denmark and Germany

In the autumn and spring, thousands of people come to the marshlands of the Wadden Sea, between Denmark and Germany, to watch huge flocks of migrating starlings take flight at sunset. The birds synchronise their movements in a flocking behaviour called murmuration. They swoop, shift and turn as one, creating incredible shapes in the sky. The Danes call this phenomenon 'sort sol', or black sun. The starling flocks can be so thick they appear to darken the evening skies. Experts believe murmuration is a defence against hawks and other birds of prey, or it could also be a way for the birds to stay warm as temperatures dip. Whatever the reason for their movements, one thing is for sure – the starlings put on a stunning show.
© Viking/Alamy