When the club-winged manakin is looking for romance, he lays it on thick with his built-in pair of violins in his wings. Until recently, no one knew how the male club-winged manakin produced its ringing love ballads. To uncover the mystery, Kimberly Botswick, curator of the bird and mammal collection in the Cornell University Museum of Vertebrates, crept into a forest in the Ecuadorian Andes with a high-speed digital video camera and spied on the small chestnut-colored birds as they tried to woo their mates.
"By examining the video at slower speeds, I could see that the males were knocking a pair of modified wing feathers together over their back at a very high rate—more than 100 cycles per second—twice as fast as an average hummingbird flaps its wings," writes Botswick in the Cornell Labaratory of Ornithology publication BirdScope.
"Although the video showed feathers knocking together, the sound the bird made was a tone. Further, the sound produced by these knocking feathers was approximately 14 times faster than the rate of the knocking itself. There had to be more to the story than what was visible in the video."
Her detective work continued back in the lab as she scrutinized the feathers of manakin museum specimens and paged through thick texts on insect communication. Then she made the discovery that put the club-winged manakin in a musical class of its own:
"I noticed seven tiny ridges on the club-shaped, hollow wing feathers for which the Club-winged Manakin is named. An adjacent feather had a kink in it that makes its feather shaft lie on top of the ridges. I had discovered the violin and bow on the feathers."
Similar to some insects, the bird's unique anatomy provides it a pair of violins built right into its wings. This is how it works, explains Bostwick:
"The wide, ridged feathers form the body of the violin and the thin, kinked feathers next to them forms the bow. When male manakins knock their wings together across their backs over and over again in a rapid cycle, the momentum from the heavier-than-usual feather shafts causes the bow feather to slide first inward across the ridged feather, then outward. This generates friction and vibration. The seven ridges generate seven knocks on the way in and seven on the way out, which adds up to that frequency multiplier of 14 needed to explain the discrepancy between the rate of feather knocking and the frequency of the sound heard. The fat hollow feather resonates at this stimulated frequency, and out comes the unique sound."
Puzzle solved: A courting male manakin is sending his sweety nothing but good vibrations. Read more about Bostwick's discovery in BirdScope.