We can now listen to songs that a small Argentinian bird thought of in its sleep. Listening to such songs across more species of birds could inform the debate on how birds dream.
Physicist at the University of Buenos Aires in Argentina got interested in the mechanics of birdsong in the early 2000s, but expected it to be just a 鈥渇un detour鈥�. Instead, it led him down the path of trying to hear what happens in birds鈥� minds. He and his colleagues have now converted the muscle activity of several great kiskadees (Pitangus sulphuratus) into audible songs.
鈥淕abriel said, 鈥業鈥檓 generating the song, the synthetic song of the [bird] dream,鈥� and I was really shocked by how similar [to birdsong] it was,鈥� says , also at the University of Buenos Aires and a co-author of the study. 鈥淚 was expecting something that maybe resembles birdsong but is much rougher. I was impressed.鈥�
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The team knew that the patterns of electrical activity in the brains of some sleeping birds match those that occur when those birds are awake and singing. In 2018, they found that this neuronal activity makes muscles in the birds鈥� throats and chests move as they do when the birds are awake and singing too. Now, the researchers have worked out how to translate that sleeping muscle activity into sound.
The researchers captured two wild great kiskadees, then used surgically implanted electrodes to record roughly 100 instances of their muscle activity both when singing and when asleep. They used these measurements as an input for a physical model of how kiskadees produce sound. That model, similar to those used by physicists to predict the sounds produced by a wind instrument, allowed them to synthesise the song that would have been produced had a sleeping bird actually been awake and singing.
The most striking song they synthesised was a distinct pattern of trills that kiskadees use during disputes over territory. When they looked at the video recording of the sleeping bird whose muscles produced this pattern, they saw that the feathers on its head stood up as if it were in a fight with a rival. Mindlin speculates that they may have, for the first time ever, recorded a bird nightmare.
But this idea assumes the birds are dreaming, which is difficult to assess. Even so, at San Francisco State University says the new study contributes to the argument that what we call dreaming can occur in animals like birds and therefore does not require human-style language. 鈥淭his research highlights what I take to be the inherently embodied nature of animal dreams,鈥� he says. 鈥淭he 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.鈥�
at the University of Utah says synthesising songs from many different bird species could shed light on why they could be dreaming at all. For birds like nightingales, which sing hundreds of different songs, comparing what they sang during daytime and what they dreamt of that night could help us understand whether they are dreaming songs to consolidate their singing skills, he says.
In line with this idea, the researchers say they are interested in expanding their bird repertoire, especially to include birds that 鈥� unlike the kiskadees 鈥� must learn and practise songs.
鈥淭he question there is what are these birds dreaming about? Are these dreams more complex or are they are still as simple as the kiskadee鈥檚?鈥� says Amador.
Chaos
