Tropical Bird Courts By Drumming

The small and colorful manakin has perplexed scientists for more than century. New research shows how this strange bird that fascinated Charles Darwin makes sound during courtship — not with song, but by beating itself with its feathers.

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STEVE INSKEEP, host:

We'll report next on the communications of birds. They're considered the premiere singers of the animal world, but there is a tropical bird that does not sing very well. Instead, it makes amazing percussion sounds with its wings.

(Soundbite of manakins' feathers)

INSKEEP: That's the mating call of the manakin. A biologist from Cornell University has recorded these sounds and figured out the birds' secret. NPR's Christopher Joyce reports.

CHRISTOPHER JOYCE reporting:

Charles Darwin knew about manakins. He saw drawings of these small, colorful birds from Central and South America. Some of the feathers had an odd shape, odder still, naturalists claim, the bird used the feathers to make weird noises. Now a century and a half later, biologists have figured out how the bird does it and why.

(Soundbite of manakins' feathers)

Ms. KIM BOSTWICK (Ornithologist): That's definitely popcorn.

JOYCE: Popcorn is how ornithologist Kim Bostwick describes the call of manakin kambia(ph). When the male wants to mate, he clears out a patch of forest floor between some branches.

Ms. BOSTWICK: When the male sees a female approaching, he lands on one of his perches and he starts to leap between them at an alarming rate. And every time he jumps between two saplings, he makes that wing sound. So while you're hearing snap, snap, snap, snap, what's happening is this bird is bouncing around on the forest floor like a maniac.

JOYCE: When these maniacs gather in a group, they sound off for passing females like players in a boy band.

(Soundbite of manakins' feathers)

JOYCE: Bostwick says the birds make these sounds by rapidly smacking together feathers that have a hollow shaft, kind of the way humans clap. There are 40 species of manakin and many variations on the drumming theme. Bostwick and fellow ornithologist Richard Prum, at Yale University, have recorded many of them. One was especially strange: Machaeropterus deliciosus, the same bird that puzzled Darwin. The shaft on a few of its secondary feathers, the ones closest to the body, had a bizarre shape.

Ms. BOSTWICK: It's more like a baseball bat where the part of the feather that attaches to the bird is the handle of the bat, and the thick, fat part on the end is the tip of the feather, and they're hollow. So that's basically the instrument.

JOYCE: Different instrument and different music.

(Soundbite of manakins' feathers)

Ms. BOSTWICK: One species, the club-winged manakin, the sound that it made was uniquely musical, atonal. It wasn't just snap. It was hmmmmm. And it's hard to understand or imagine how a bird could possibly make a sound like that.

JOYCE: Bostwick took her camera and recorder to the rain forests of Ecuador to find out. She soon encountered a group of males.

(Soundbite of manakins' feathers)

Ms. BOSTWICK: And you can hear that tick, tick hmmm. So apparently I had really caused a stir by walking into this territory.

JOYCE: Her high-speed camera captured the bird in action.

Ms. BOSTWICK: Imagine the wings are like open in like a soaring position. Now tip the wings up so you're seeing the top surface of the wing pointing forward, and this is where you see those feathers going knock, knock, knock, knock at about 110 cycles a second, which basically blows any other bird or vertebrate-wing or limb movement out of the water. It's super fast.

(Soundbite of manakins' feathers)

JOYCE: That wing flapping explained the tick, tick. But how did the bird make that final humming ting? It didn't sound percussive and when Bostwick measured its frequency, it came in at about 1,400 cycles per second. That's about 14 times as fast as the wing beats she filmed. It didn't add up. The answer lay at the tip of two of the bird's feathered shafts. One had a row of seven tiny ridges, like a washboard. The little feather next to it tapered into something that resembled a guitar pick.

Ms. BOSTWICK: Every time that bird is knocking the feathers together, that little feather is sliding over the tip of the feather next to it, then going bump, bump, bump, bump, bump--seven times on the way in--bump, bump, bump, bump, bump--seven times on the way out.

(Soundbite of manakins' feathers)

Ms. BOSTWICK: And that sets off vibrations in that hollow shaft of that fat feather and, boom, you've got a sound at 1,400 cycles a second.

JOYCE: Writing in the journal Science, Bostwick and Prum note that lots of birds have grown colorful feathers or learned elaborate song and dance routines to attract mates, but only the manakin has turned its body into a percussion instrument.

Christopher Joyce, NPR News.

INSKEEP: This is NPR News.

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