Common Snipe drumming

The sound of the Snipe's drumming display flight is a common feature of early morning walks on the moors but they can be surprisingly difficult to see as the aerial display is usually high in the sky. 
The drumming sound is created by fanning the outer tail feathers during a rapid dive and is the sound of the wind passing these feathers. In normal flight the feathers are retracted and the vibrating sound stops.

Snipe in drumming display