Most male birds attract mates and proclaim territories by singing with the help of a voice box, or syrinx, located in the windpipe just above the heart. But a variety of species augment vocal sounds by producing “mechanical communication signals,” using portions of their anatomy to create sound. For instance, woodpeckers drum rapidly on resonant wood with their beaks to alert other woodpeckers of their whereabouts. And hummingbirds court by flying rapidly to and fro, making high-pitched metallic sounds caused by air vibrating off their stiff wing feathers. But to me, the most amazing of all mechanical bird sounds is the drumming of the Ruffed Grouse, a chickenlike bird that inhabits deciduous and mixed forests from northern Georgia all the way to Alaska.
In the spring, male grouse perch on fallen logs in the forest, often arriving before dawn’s light. The male begins his drumming display by bracing his tail, puffing up his breast, and ruffling his neck feathers. Then he opens and closes his wings in rapid succession, producing very low-pitchecd thumps at a frequency of only 60 cycles per second (= 60Hz). The thumping starts out slow but quickly gains in speed, and the rapidly beating wings turn into a complete blur as the drumroll reaches its peak.
How on earth does the grouse produce such an unusual sound? Early investigators assumed that the thumps were caused by compression of air against the male’s breast as the wings were suddenly drawn inward, like Tarzan beating on his chest. But this is incorrect: the thumps are actualy little sonic booms created as air suddenly rushes to fill a vacuum made when the wings are thrust outward from the breast. Regardless of how the sound is made, grouse drumming is amazing to behold, a low-pitched marvel that is often felt more than it is heard.
(the above text is excerpted from The Songs of Wild Birds, a book-and-CD by Lang Elliott, published by Houghton Mifflin Harcourt.)
Below is a recording of a single drum of a male. Notice all the low frequency content and also the interesting timing. The drum gradually speeds up, but unevenly at first. This timing pattern is typical of the species, at least in Eastern North America, and there are only minor variations among the drums of a single male (note: drums are so low-pitched that you may not hear them unless you listen with headphones or play through speakers accompanied by a subwoofer):
Ruffed Grouse drumming_5am_17 April 2009_Connecticut Hill State Game Management Area near Ithaca New York_Recorded by Lang Elliott.
NOTE: Our Ruffed Grouse video features footage gathered in late March and early April 2009 at the Connecticut Hill State Game Management Area near Ithaca New York (see map below). Bob McGuire and I located at least five drumming logs, but only one of them ended up being productive for us. That log was situated right next to a dirt road and the resident male was well-habituated to passing cars and other disturbances. This worked to our advantage. While most footage was obtained using a portable blind, my favorite sequence of the grouse drumming during a snowstorm was made from my parked car! Along with gathering our own video and sound, my friends Marie Read and John Cancalosi both photographed the grouse, and Martha Fischer of the Cornell Lab recorded his drumming.
Connecticut Hill State Game Management Area