Male ruffed grouse “drum” in springtime as a way to establish territory and to attract females. Although it looks as if the sound is caused by the bird’s wings hitting its chest, the sound actually comes from small sonic booms. The wings beat up to 5 times per second, causing the sound waves to stack up until they create a penetrating shock wave that creates the boom. Male grouse usually perform on a “drumming log,” which might help project the low-frequency sound. Drumming exerts a remarkable amount of energy, and a male might lose 10 percent of its body mass during mating season.
