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Songbirds couple up to stay in tune

fortune1HR.jpgPosted on behalf of Arran Frood

They say it takes two to tango. And when plain-tailed wrens sing a duet, it seems that the songs made by male and female partners are indeed like a dance: each individual reacts to the other’s notes as dancers do to their partner’s footsteps.

“Dancing is the perfect analogy,” says lead author Eric Fortune of Johns Hopkins University in Baltimore, Maryland. “The same types of interactions occur between two birds singing and a man and a woman dancing.”

In the first study to measure the brain activity of duetting songbirds, published in Science today, researchers also found that the females take the lead, whereas males are most likely to make mistakes.


Male and female plain-tailed wrens (Thryothorus euophrys) are thought to duet to defend territory. When they sing together, they each alternate between notes so rapidly it sounds like a single bird song. But because these birds also sing alone, the researchers weren’t sure if each bird simply sings a fixed, pre-arranged pattern — two combined solos — or if the duet is a cooperative, reactive effort.

To find out, Fortune and his colleagues captured more than 1,000 wren songs in 150 hours of recording at the Yanayacu Biological Station and Center for Creative Studies, some 2,700 metres up the slopes of the Antisana volcano in Ecuador. They found tiny differences of just tens of milliseconds in the timings of syllables in solo songs compared to duets, meaning a tighter sound when the songs were sung together. They also found that male songs were more variable and that males were more likely to drop a song while the female continued — indications that the females were orchestrating the music.

Watch a video of Fortune explaining his songbird study.

The researchers then measured the birds’ neurological responses to different songs by attaching electrodes to a part of the brain known as the higher vocal centre (HVC), which Fortune describes as a selection of specialized neurons for the control of song learning and production. They played male, female and duet songs to male and female birds and recorded the resulting activity in their HVC.

Based on previous studies of other, non-duetting songbirds, the researchers expected that each bird would respond most strongly to its own song part — much as a dancer is most familiar with his or her own steps. In fact, both male and female birds reacted most strongly to duets. “Animals that cooperate together have an understanding, a form of memory in their brains of that cooperative performance,” says Fortune.

Both male and female brains also reacted more strongly to female songs than to male ones — another sign that females take the lead in duets. “His representation of her part may help him to coordinate with her and his goal may expressly be that.”

Fortune says the research could be applied to robotics, to help robots respond more sensitively to other individuals, including humans, that they interact with. “Shaking a robot’s hand is dangerous,” he says. “We’re proposing to transform how roboticists develop models for cooperative output.”

Image shows male plain-tailed wren, courtesy of Eric Fortune and Melissa Coleman. Video courtesy of Science/AAAS.

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