Barwick, Biebrza National Park,
22' 14.5'' N 22º 33' 32.4'' E
3 July 2009, 2025h
Advertising sound of a bird in aerial display flight
(drumming) - a non-vocal sound produced by the rush of air over
the bird's outer tail feathers. Flying a circuit c100 metres in
diametre and 'diving' 4-5 times per minute. Note the striking pattern
created by the harmonics from 0.22 kHz to over 8 kHz.