Scientists Translate Sleeping Birds’ Silent Songs Into Sound—and They May Have Recorded a Nightmare

Using surgically implanted electrodes and modeling, researchers brought to life the vocal muscle activity of sleeping great kiskadees

Bird with yellow feathers on belly
Scientists brought to life the silent, sleeping songs of two great kiskadees. Andrej Chudý via Flickr under CC BY-NC-SA 2.0 DEED

While birds are fast asleep, their brains remain active, firing off electrical signals that can mimic those that occur while they’re awake and singing. This silent brain activity can even make the vocal muscles in their chests and throats move—similar to the way a sleeping dog’s paws might twitch.

Now, for the first time, researchers have translated birds’ sleeping muscle activity into sound. The findings, published this month in the journal Chaos, offer new insights into the avian brain, as well as clues to what birds might dream about as they snooze.

Researchers set up an experiment involving two great kiskadees—small, brightly colored flycatchers that live in South America, Central America and parts of Mexico and Texas. The birds have vibrant yellow feathers covering their bellies, brownish-orange wings and a black-and-white “bandit’s mask” on their faces.

After capturing two wild birds, the scientists used surgically implanted electrodes to record the creatures’ muscle activity while they were sleeping and awake. In total, they recorded about 100 instances of muscle activity associated with singing.

The team created a model to predict which types of muscle activity produced which sounds. Then, they used the model to bring the birds’ silent, sleeping songs to life.

One of the synthetic songs they produced matched the noises kiskadees make when fighting over territory. When they went back and looked at video footage of the sleeping bird from that moment, they noticed its head feathers were standing on end—just like they would if the bird had been awake and sparring with a competitor.

It’s possible the bird was having a bad dream, says study co-author Gabriel Mindlin, a biophysicist at the University of Buenos Aires, to Science Friday’s Maggie Koerth.

“You could figure out this guy was experiencing a nightmare probably, recreating the whole experience of having a fight in his sleep,” he adds.

Great Kiskadee Calling and Feeding

Even after documenting muscle activity, it’s difficult for scientists to prove the birds were experiencing dreams. But even if birds don’t dream the exact same way humans do—with language and self-awareness—the findings suggest something is going on inside the minds of slumbering non-human creatures.

The new study highlights “what I take to be the inherently embodied nature of animal dreams,” says David Peña-Guzmán, a philosopher at San Francisco State University who was not involved with the study, to New Scientist’s Karmela Padavic-Callaghan.

“The kinds of memories that are involved in [animal] dreams are more procedural than declarative, [meaning] they have more to do with the performance of bodily skills and less with linguistic realities,” he adds to the publication.

Previous research found sleeping pigeons experience brain activity in regions linked to visual processing and signals from the wings—suggesting the common city birds might dream of flight. And zebra finches vibrate their vocal cords in a way that makes it seem like they’re practicing songs.

In the future, the great kiskadee researchers might expand their experiment to other types of birds—including those that sing a wide array of songs depending on the scenario. Matching those birds’ silent, sleeping muscle activity with each song’s use during wakefulness could offer even more insights into their dreams.

In addition, scientists might be able to use this study as a jumping off point for one day interacting with sleeping birds. The findings might also spur studies about the role sleep plays in learning.

For now, however, the findings serve as a reminder that humans are not so different from other animals—even those that look and act nothing like us.

“Knowing that we share [dreams] with such a distant species is very moving,” says Mindlin in a statement. “We have more in common with other species than we usually recognize.”

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