UC Berkeley
After comparing her observations of the red-capped manakin with published observations, Kim realized that the descriptions of these birds from the literature could not address the sort of evolutionary questions she was asking. Without high speed video and acoustic sonograms (pictorial representations of sound waves), other observers had lumped distinct noises, produced in different ways, under the same name — a “klock.” In fact, the red-capped manakin produces five distinct wing sounds at different points in its mating dance.
To get data detailed enough to map onto her tree, she would need to observe more birds firsthand, a task that took her all over South and Central America — and, coincidentally, satisfied her wish from early graduate school to travel to exotic locales.
When Kim returned to Ecuador, she was able to get high-speed video of the club-winged manakin that helped explain what in the world it was doing with its wings. The video revealed that, to produce its violin-like hum, the bird was knocking its wings together at a rate of 107 knocks per second — faster than the fastest hummingbirds, which typically flap their wings at around 75 cycles per second when they are excited. But the noise that the manakin makes is a continuous (but brief) hum, not a series of knocks. Furthermore, the sound has a pitch of the F sharp above high C. That’s about 1500 cycles per second, 14 times faster than the rate the bird moves its wings! How does it get from 107 knocks per second to 1500 cycles per second? The answer grew out of the anatomical studies that Kim did when she first started this project. The club-shaped feather of the club-winged manakin has seven ridges on it. When it knocks its wings together once, the adjacent pick-shaped feather rubs over the ridges like a washboard — once on the way in and once on the way out — for a grand total of 14 bumps. When 14 bumps are raked over like a washboard at the rate of 107 times per second, it produces a noise of about 1500 (14 x 107 = 1498) cycles per second — music to any female manakin’s ears…
