This makes the background feathers shimmer but the eye spots stay still
Vibration frequency also generatesthe characteristic rattling sound
The effect is mesmerising to the female, and demonstrates male virility
It may be one of the most obvious and best loved courtship displays in the natural world, but the extravagant tail feathers of the peacock are only now revealing just how captivating they are.
As the male shakes his long and colourfultail in a bid to woo his mate, the feathered eye spots remain stationary against a backdrop of shimmering plumes.
This effectively hypnotises the female, leaving her powerless to resist the male's attentions.
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To achieve this remarkable effect, the males exploit thephenomenon of resonant frequency.
By shaking their tails at the same speed as their natural resonance, the feathers are vibrated with the greatest amplitude but the brightly coloured eyespots remain practically motionless.
Using high-speed video, team of zoologists led by Roslyn Dakin at the University of British Columbia found that peacocks 'stridulate' or rattle their tail feathers at an average 25.6 Hz.
This generates a broadband, pulsating mechanical sound.
All objects have a natural harmonic frequency at which they vibrate if not fixed in place.
Smaller objects have a higher resonant frequency and vibrate faster, generating a high-pitched noise - such as a bicycle bell, which rings at a higher note than a church bell.
Peacock tail feathers have resonant frequency lower than the lowest string on a bass guitar and only a little higher than the 20 Hz lower limit of human hearing.
As an object such as a guitar string or peacock feather vibrates, certain locations called nodes along its length remain stationary, while the sections in between move with higher amplitude.
Laboratory tests revealed this was the resonant frequency for the feathers, and that the eye spots were located at the resonant nodes.
The result is that, when the tail is shaken, a characteristic rattling noise is generated and the bright eye spots remains almost motionless against an oscillating iridescent background.
The birds had one further trick up their tails, within the structure of the eyespot feathers.JournalPlos One. Read more :