Cloud of Birds
A large flock of Common Starlings (Sturnus vulgaris) in early morning fog.
Huge flocks of more than a million Common Starlings may be observed just before sunset in spring in southwestern Jutland, Denmark over the seaward marshlands of Tønder and Esbjerg municipalities between Tønder and Ribe. They gather in March until northern Scandinavian birds leave for their breeding ranges by mid-April. Their swarm behaviour creates complex shapes silhouetted against the sky, a phenomenon known locally as sort sol (Black Sun). Flocks of anything from five to fifty thousand Common Starlings form in areas of the UK just before sundown during mid winter. These flocks are commonly called murmurations