(ANIMAL MATING) How do male hummingbirds capture the eyes of potential mates? While their melodious voices and colorful wings first come to mind, the sound of their wings flapping helps males attract females. Read on to learn more about how tail sounds help hummingbirds find their true loves! — Global Animal
The New York Times, Andrew Revkin
David Rothenberg, a musician, author and environmental philosopher (and friend and neighbor last seen here covered in cicadas), has contributed a “Your Dot” reflection on some fascinating research published in the Sept. 9 edition of Science. The work reveals how the males of certain hummingbird species go beyond the usual avian song-making methods, exploiting the turbulence around tail feathers to add to their conventional vocalizations when trying to attract a mate.
Here’s a video explainer from Science by the lead author of the paper, Christopher J. Clark of Yale University, who’s been studying the evolution and dynamics of hummingbird tails for a long time:
Here’s the reaction to this “feather music” from Rothenberg, whose latest book, “Survival of the Beautiful: Art, Science, and Evolution” (to be published next month), explores instances of what might be called aesthetic evolution:
If you’re a male hummingbird, singing your song is not always enough. Sometimes you have to play the same tune with your tail, by plummeting through the sky while letting your tail feathers do the singing.
In a paper published today in Science, Christopher J. Clark, Damian Elias, and Richard Prum explain this unusual method of sound production for the first time: “We show that these sounds are produced by air flowing past a feather, causing it to aeroelastically flutter and generate flutter-induced sound.… Neighboring feathers can be aerodynamically coupled and flutter either at the same frequency, resulting in sympathetic vibrations that increase loudness, or at different frequencies, resulting in audible interaction frequencies. Aeroelastic flutter is intrinsic to stiff airfoils such as feathers and thus explains tonal sounds that are common in bird flight…. Although aeronautical engineers take extreme precautions to avoid flutter and its catastrophic consequences for aircraft, birds have instead repeatedly evolved novel acoustic communication signals from these incidental vibrations.”
The Costa’s hummingbird, native to the Southwestern United States, makes a sound with its tail feathers almost identical to the song it sings in courtship. Why would it need to make both?
“Females like the sound,” says lead researcher Chris Clark. “They don’t care how the sound is made.” He hypothesizes that the vocal sound may have evolved from the tail sound, since bird sounds are often learned, while bird displays are thought to be innate. [Links are to sound files.]
Why does a bird evolve one kind of sonic preference rather than another? Here we enter the realm of evolutionary aesthetics, something co-author Richard Prum has been recently investigating. “Why should a bird that is totally outfitted with a perfectly fine vocal organ evolve an entirely novel way of making the same sound, with its feathers? Many ecologists think that the point of performance is the exhibition of skill and exertion, rather like imagining that we like a violin concerto because the violinist has to sweat to play it fast enough.”
Prum believes, instead, that the females have evolved to like this particular sound, a rising and falling whistle. “I rather think that the exertion and skill are merely a means to the end. What intrigues them will ultimately evolve, but what they will find intriguing is as unpredictable as next years fashions.”
The female birds must hear exactly the right sound to be impressed. The qualities of that sound define musical beauty as understood by the Costa’s hummingbird. It doesn’t matter what the sound is, only that the females have evolved to need it.
Yet that rise and fall is not an unfamiliar pleasure in the animal world. It sounds almost exactly like the song of the bowhead whale, a rarely encountered denizen of arctic seas. Why such sonic parallels between species way far apart on the tree of evolution? There may be more to animal aesthetics than arbitrariness…
As an addendum, I would love to know who’s probing the amazing courtship sounds and behaviors of the woodcock — which we were lucky to observe (and record) at close range in our yard for several years.