Peacocks make fake sex sounds to attract females' attention, scientists say.
The birds are known for shaking their tail feathers but Canadian researchers have revealed a further sexual tactic.
Peacocks have a wide vocabulary of calls, and during mating they make a distinctive hoot.
Biologists also recorded males making this sound when out of sight of females and suggest such deception could prove rewarding for the birds.
The findings are published in The American Naturalist.
Peacocks are one of the most obvious examples of advertising sexual fitness in the animal kingdom with their eye-catching plumage and strutting courtship displays.
The mating behaviour takes place in open areas of land referred to as a 'lek'.
When a male has successfully attracted a female, or peahen, it rushes at her making a distinctive hooting call before attempting to mate.
These calls are loud enough to be heard from a distance, prompting scientists to investigate what benefit this has.
'It's much louder than it needs to be to communicate with just the female that the male is trying to mate with,' explained Dr Roslyn Dakin from the University of British Columbia, Canada, who co-authored the study.
Dr Dakin studied groups of birds living freely and unmanaged in zoos and parks across North America where they were introduced from their native India.
Across the groups, she found that males would make the 'copulatory call' when they were nowhere near a female, yet females would be attracted over to the lek by the sound.
Dr Dakin found the fake calls to be 'surprisingly common' among 60% of the males. The 'faking males' were also the most prolific breeders in the group.
She suggests these males may have learned that the deception brings the reward of female company.
'We know that sound increases the chance a female will come around and visit the male but what we don't yet know is whether males get any fitness benefit from that,' she said.
If the fake hoot does result in successful mating, the biologist suggests this could be evidence of the birds using a 'dishonest sexual signal'.
By pretending they are mating when they are not the birds could convince females they are more sexually active - and therefore genetically fitter - than their rivals.
But this sort of deception is thought to be rare in the animal kingdom because it can result in a poorer genetic legacy. It is considered 'costly' for females to invest their energy in raising young that might not produce further generations.
Such deception also risks the signal being ignored entirely by females that have heard it too many times.
'We found that a third of the calls were fake, which is astonishing,' said Dr Dakin.
'Theory predicts that when faking happens a lot, the receivers should stop listening to the fake signal at all. So what is it that's allowing this deception to persist at such a high rate?'
According to Dr Dakin, deceptive calls could be more common in the animal kingdom than previously thought.
The next phase of her research will investigate whether there are any direct reproductive benefits for males that make fake sex hoots.
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