A good magician knows the secret of a quick getaway – create an illusion! And it seems like some Australian birds are feathered Houdinis when it comes to distracting predators.
Some birds only flash their colours when they are moving, creating the illusion that they are a different animal. A new study, published in Proceedings of the Royal Society B, suggests this is to confuse predators into thinking they have the wrong target.
This technique is called flash-display – the hidden colours may be under the wings or feathers and are only visible when the animal is taking off and flying away. When the bird is settled it looks one colour – called its cryptic state. But when it is moving it displays another – a conspicuous state.
However, the reason why some birds displayed this trait was unclear.
To answer this question, a team of researchers, led by Karl Loeffler-Henry of Carleton University, Canada, used computer simulations and real-life examples of Aussie birds to test how well birds would survive in different situations.
They found that flash-display worked best if the birds flew off when the predator was still at a distance and couldn’t see clearly, creating the illusion of a completely different animal.
The closer the predator, however, the more likely it was to realise the flash-display was just a trick.
“Flash behaviour may serve several functions which are not mutually exclusive, but if it acts as an illusion – deceiving the predator into believing the signaller is always conspicuous when in fact it reverts into its cryptic state once it has settled – then it helps if the magician does not show his hand,” says co-author Thomas Sherratt of Carleton University.
“If the predator sees the signaller switch from being cryptic to conspicuous as it flees, then the predator will be more aware that the prey has two colour patterns and adjust its search appropriately.”
After running the computer simulations, the team used data from 63 Australian birds to see if the flashers were also trigger-happy when it came to flying away.
“To our knowledge, Australia does not have a preponderance of avian flashers!” says Sherratt. “Australian birds were chosen simply because well-replicated data were available from Dan Blumstein under standardised conditions.”
Using this data, they found the birds who fled quickly were more likely to flash-display, suggesting that the illusory technique worked best from a distance.
Deborah Devis is a science journalist at Cosmos. She has a Bachelor of Liberal Arts and Science (Honours) in biology and philosophy from the University of Sydney, and a PhD in plant molecular genetics from the University of Adelaide.
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