Biologists have known for some time that peacocks use their shimmery, iridescent feathers to woo partners (known as peahens) — but they now have a better idea of what the frenzied feather shaking looks like to potential mates.
University of Manitoba biologist James Hare studies animal behaviour and communication and has had his eyes on the free-roaming peacocks at Assinboine Park Zoo for a few years now.
"When I started watching peacocks at the zoo, I could see kind of like a standing wave set up in their train as they displayed. You could see the oscillations of the train itself," Hare said.
Hare and U of M graduate student Angela Freeman previously discovered peacocks emit a deep rumble from those shaking "train" feathers during courtship displays that is inaudible to the human ear.
Hare said some work suggests the birds are hearing the sound, but it's also possible they're feeling the bass.
"When you get low frequencies, you can actually feel the rumbling," Hare said.
In a study published Wednesday, University of British Columbia biologist Roslyn Dakin, Haverford College physicist Suzanne Amador Kane, Hare and others built on those findings and say they've figured out what role tiny specialized feathers play in the elaborate fanning and rumble.
Researchers recorded the low frequency sounds and played them back to the birds using a heavy duty subwoofer. Both peacocks and peahens responded to the sounds, Hare said.
They filmed the experiment using high-speed video, and when they reviewed the tape, found out more about how those mesmerizing eyespots manage to stay remarkably still amid the wave of feathers, which vibrate at a rate of 25 times per second.
The eyespots are areas of great density in the train, where small barbules (a filament that extends out of a feather) are linked together with micro-hooks, Hare said. Those roughly 130 eyespots or "nodes" are held together tightly and enhance the sound and sight of the display.
"The eyespots appear to remain motionless against this background of a shimmering feather mass," Hare said.
Understanding the basic bio-mechanics of the display could lead to further research on how the "signal characteristics influence female choice of males," Hare added.
"Now we know there's a lot more to it — more than meets the eye."
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