Biology Reference
In-Depth Information
Q Once I was walking in the woods and heard a soft, low thumping sound that got
faster as I listened. I couldn't see what was making the sound, but a friend told me
it was a Ruffed Grouse. Is that true?
A
Yes, male Ruffed Grouse produce a distinctive drumming sound, beginning slowly at
first but speeding up into a whir. Because grouse often stand on a log while doing this,
people once believed this sound was produced by the grouse's wingtips beating the log
— or that the bird thumped its wings against its breast, Tarzan-like.
Butin1932,ArthurA.Allenhidoutnearagrouse'sdrumminglogandcaughtagrouse
on film with his slow-motion movie camera. The stopped frames of the film showed that
the grouse stood crosswise on the log, braced on his tail, and cupped his wings, bringing
them forward and upward with such force that he compressed a parcel of air between his
chest and wings, creating the sound wave without touching his wings to his chest or to
the log. The sound is deep, about 40 hertz, which is at the low range of human hearing,
explaining why some people say they almost “feel” the sound as much as hear it.
In spring, Ruffed Grouse males declare their territories and announce their presence
to females by drumming. Although drumming peaks in April or May, they may drum at
any time of year. In fall, you can often recognize a young grouse by his pitiful attempts
at drumming. Until a bird masters the trick of cupping the air properly, he may simply
produce a dull flapping sound, but as with many skills, practice makes perfect.
If the idea of producing such a sound simply by compressing air in the “wingpits”
seems hard to imagine, remember that humans can also produce a sound in our armpits
by compressing air. There's one notable difference between Ruffed Grouse and humans,
though — female grouse find their partners' “pit” sounds attractive.
