It's definitely not for our ears: Peacocks make low rumbling love calls with their feathers when they spread their brilliant tail fans in a courtly display.
The lovelorn vibration turns out to be a turn-on for peahens whether she hears it from close up or far away.
We just can’t hear it.
And with that, a University of Manitoba student discovered a new scientific truth that birds, specifically peacocks, make sounds which are undetectable to human ears. Up until now scientists thought we could hear every chirp, cheep and bleep that birds around the world can make.
It took graduate student Angela Freeman to learn that when male peacocks display their feathers they are also making deep rumbling sounds that are too low-pitched for humans to hear.
Freeman, a biology student, is the first person to discover a bird that makes and perceives noises that are inaudible to humans. She reported her finding at the annual meeting of Animal Behavior Society on June 13.
The sounds are songs created by audible vibrations as a peacocks fans out his feathers in a display. And there are two courting displays, one called the "pulse train" and the other called the "shiver train."
And either one can make a peahen swoon.
The shiver train is produced by vibration of the train feathers from the centre feathers to the outside of the array. It’s used by males when females are far away.
The pulse train is produced by a vibration emanating from the base of all the train feathers and it is used when the female is nearby.
Upon witnessing either of these, though, all a human would hear is a leaf-like rustling of the feathers.
Other animals, such as elephants, have long been known to produce such infrasound (sounds below 20 hertz), which humans can’t hear. And although a type of grouse called the capercaillie produces infrasound, it so far seems that those birds don’t communicate with it – they either can’t hear it themselves, or they just don’t care about it.