Fairy-wrens eavesdrop to avert danger

By Natalie Muller | August 18, 2011

Superb fairy-wrens steer clear of danger by listening in on the warning cries of other birds.

AUSTRALIAN RESEARCHERS HAVE DISCOVERED that crafty fairy-wrens can understand and respond to the danger calls of other birds, suggesting that they have an advanced level of awareness about the world around them.

When behavioural ecologist Dr Robert Magrath and biologist Thomas Bennett – from the Australian National University in Canberra – played a recording of the ‘hawk’ warning call employed by the noisy miner bird (Manorina melanocephala), they observed the tiny wrens speedily fleeing to safety.

Their research, to be published in an upcoming edition of the journal Proceedings of the Royal Society B, shows that superb fairy-wrens (Malurus cyaneus) aren’t just reacting to the sounds, but rather, they have developed a sophisticated understanding of the meaning and urgency of various warning tweets.

“It means they can take advantage of a sort of neighbourhood watch system – and if another species spots danger and calls, and if it can recognise that call, it gets an early warning of danger,” says Robert. He adds the fairy-wren’s ability is impressive, considering warning calls are different within each species.

Paying heed to the cautionary cries of others isn’t unique behaviour. Studies show many species, such as the white browed scrubwren (Sericornis frontalis) and new holland honeyeater (Phylidonyris novaehollandiae) react to each other’s alarm calls. But the team’s investigation suggests the fairy-wren’s perception runs deeper.

Fairy-wrens heed warning sounds

The researchers challenge the long-held belief that birds respond to alarm calls because they sound scary, high-pitched and loud. Instead, they argue, fairy-wrens living near miners become familiar with their warning sounds – a feat comparable to learning part of another language.

“If the wrens are familiar with the miners, then they apparently learn that those sounds mean danger. When you play back the sounds, they dash for cover because they’ve learnt about the meaning of those calls,” Robert told Australian Geographic.

When the recordings were played in parts of Canberra where miners are not found, the researchers observed that the fairy-wrens appeared to ignore the calls.

Behavioural ecologist Dr Michelle Hall from the University of Melbourne says the study is interesting because it looks at the broader picture of cross-species communication.

“We know already that superb fairy-wrens are like many territorial songbirds in that they respond aggressively to the songs of other superb fairy-wrens, but this study shows that they also pay attention to the wider community,” she says. “The really interesting point is that they learn who is worth paying attention to.”

Fairy-wrens learning the call

Robert says the spread of noisy miner birds across Australia in recent decades is something fairy-wrens, found in the country’s southeast, use to their advantage. “Miners are pretty useful because they live in trees, so they’re really good at spotting danger in the distance, kind of like an early warning,” he says.

But little is known about how wrens pick up alien warning sounds. Robert says it’s likely they learn as young birds, observing how their parents react to different noises. However there is also evidence they can adapt and learn later on in life as well. “Female fairy-wrens always leave where they were born and go somewhere else to breed, so it’s probable that they also learn as adults,” says Robert.

A closer examination of how long this learning process takes will give us a better idea of how the fairy-wren can survive and adapt in changing environments, he says.

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