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.