ScienceWise - Spring 2011

Head banging to bird song

Can different bird species understand what each other are saying?

He spends half his time listening to heavy guitar riffs and the other half tuning in to the pleasant twitter of birdsong. Tegan Dolstra speaks to Trevor Murray, dreadlocked ANU PhD student and heavy metal fan, about the hot topics in bird communication.

Within the grounds of Canberra’s Australian National Botanic Gardens, entire conversations are taking place, unintelligible to the human ear. A cacophony of bird song fills the air, from the delicate trill of the wren, to the raucous squawk of cockatoos.

The Research School of Biology’s Trevor Murray is shedding some light on the remarkable way birds gather information by ‘eavesdropping’ on their neighbouring species’ chitchat.

Understanding other species’ ‘languages’ is sometimes more useful, safe and easy than listening to your own species or sourcing the information yourself.

“The birds all listen to each other,” Trevor explains. “We’ve got this really cool system here in Canberra where we can look at the interactions between Superb fairy-wrens and White-browed scrubwrens, which both give alarm calls when predators fly overhead. As well as fleeing to cover when they hear their own alarm calls, they also respond to the other species’ alarms.”

Trevor wanted to find out just how easily scrubwrens and fairy-wrens listen in on each other.

“There’s this intuitive idea that it’s harder to understand other species: humans can understand one another pretty well, but we can’t really understand what our dogs are saying. We expect it’s the same for birds too,” he says.
After many days playing recordings of alarm calls to birds and observing their response, Trevor found that they did indeed have more trouble understanding the other species. He also discovered an intriguing difference in the way fairy-wrens and scrubwrens react to alarms.

“The really interesting thing is that the fairy-wrens responded differently to the scrubwrens. Whereas scrubwrens are just as likely to flee when they hear a fairy-wren alarm as when they hear their own alarm, fairy-wrens, on the other hand, are more likely to ignore a scrubwren alarm.”

Trevor thinks this difference in behaviour might be down to how familiar each species is with its neighbour’s call.
“If you meet someone with a heavy accent for the first time, you might not be able to understand what they’re saying,” he says. “Already being familiar with the accent will help.”

“Fairy-wrens generally give alarms more often than scrubwrens. My idea is that because scrubwrens are more likely to hear a fairy-wren alarm than vice versa, they are more familiar with it and can more easily understand what it means.”
Trevor also tested whether low volume or degradation of the alarm (due to the sound bouncing off undergrowth, for example) hampered the birds’ ability to understand their own alarms.

“We found that the quieter the alarm (the longer it’s travelled to get there), the less likely the birds are to respond,” he says. “On the other hand, degradation had no effect on alarm response.”

Trevor’s conclusion is that these alarms have evolved to be work over a short range.
“Over the normal distances these animals would be communicating - at most 10 or 20 metres - degradation doesn’t really come into play,” he says.

Growing up in Griffith, a country town in NSW, science was Trevor’s favourite school subject. For a Year 10 project he designed an animation of the molecular workings of DNA transcription.

Not realising how much he enjoyed biology, Trevor moved to Canberra to study video games programming. His interest in biology was reignited through a part-time tour guide job at the National Dinosaur Museum and he enrolled in a Bachelor of Science/Computer Science at the ANU.

Between listening to birds and heavy metal (his favourite band is Nile) and watching TV and movies, Trevor still spends most of his spare time playing computer games. He’s even found a way to combine his two passions at work, putting his computer skills to use helping his scientist colleagues with programming. I wonder if he’s also a fan of Twitter?

(by Tegan Dolstra)

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