Black cloud

During spring in Denmark, at approximately one half hour before sunset, flock of European starlings (Sturnus vulgaris) that the number could reach more than a million gathered from all over come together to form amazing formations.

This phenomenon is often called the Black Sun, and can be found in early
spring along the marshy land in the western part of Denmark during March to mid April. These birds migrate from the south and spent his time in the pastures for food and sleeping on the grass at night.

You can see the video about the balck cloud below :