Chris Davies - Apr
12, 2018
You might think being able to
hover in place and dip your long, stealthy beak into the sweetest nectar would
be enough as a male hummingbird to attract a mate, but it turns out female
Costa’s hummingbirds are a little more demanding. Scientists researching the
birds have observed unusual flying patterns, in which the male birds produce an
unexpected type of song: from their tails.
Unlike regular birdsong, the male
Costa’s have developed a new way to sing to potential mates. Researchers at UC
Riverside used an acoustic camera to record how the birds flew around,
observing that whereas most male hummingbirds would dive in front of the
females, the Costa’s opted to fly to the side instead.
Turns out, it’s sound not speed
that they’re trying to demonstrate. By twisting their tails up vertically, by
as much as 90-degrees, the birds can cause the outer tail feathers to flutter
and create a “song” of their own. However there’s also a sly reason for it,
that goes beyond merely music.
The careful twisting and diving
also allows the birds to minimize the Doppler effect as they whoosh past their
preferred mate. That’s the same effect that changes how a sound is perceived
depending on whether it’s moving toward you or away from you. You’ve probably
noticed, for example, how the sound of the siren from an ambulance or fire
truck alters once it goes past you.
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