Double Drum - Male Ruddy Duck
Not a fabulous image technically, but I like what it shows: the results of the rapid drumming of the male's breast feathers with its broad bill by which the duck presses air from under its breast feathers. In this case, two shock waves of air-filled water radiate out from the duck from successive drumming motions. A third wave has already dissipated. About about 5 - 8 total beats would be done each time, but not all result in such clean looking waves.
Double Drum - Male Ruddy Duck
Not a fabulous image technically, but I like what it shows: the results of the rapid drumming of the male's breast feathers with its broad bill by which the duck presses air from under its breast feathers. In this case, two shock waves of air-filled water radiate out from the duck from successive drumming motions. A third wave has already dissipated. About about 5 - 8 total beats would be done each time, but not all result in such clean looking waves.