Birds given the pain reliever fentanyl in low doses produce a "sociable" song that "sounds like freeform jazz," one study shows.
Researchers at the University of Wisconsin, Madison, theorized that when birds sing, opioids are produced in their brains that give them pleasure.
To prove their theory, they gave the starlings a drink of fentanyl – an opioid used as a pain reliever and recreational drug – and then listened to their song.
They found that when birds sing for pleasure, rather than marking territory or finding a partner, the singing is "sociable" and sounds like jazz.
Biologist Lauren Riters and colleagues found that the post-opioid drug song was the same type of sound birds make when they come together in a flock.
"When they practice, they try different songs, they order and rearrange song sequences and repeat them, they add notes and put them down," Riters said.
“It sounds a bit like freeform jazz and is very different from the structured songs male songbirds produce when trying to attract partners.
"It's the freeform songs that are produced during training that our studies find rewarding."
Researchers at the University of Wisconsin, Madison, found that birds that sing in flocks rather than for mating purposes are "gregarious" and bring them joy
Previous studies of bird song have focused on how it's produced and why it evolved in the first place – but this is the first to look into why they sing.
To better understand the underlying pleasure birds get from warbling, Riters examined the behavior of a group of European starlings.
The researchers decorated an area and put the birds in after they sang, and later gave them the choice of returning that area or an undecorated room.
The birds stayed longer in the decorated area, suggesting that they associated this with the joy of singing.
"It's evidence that a positive state is induced by the presence of herdmates, which stimulates the song, and that birds continue to produce sociable song because it's worth it," Riters said.
“Although male songbirds are known to sing when they are not around other birds, for example when defending areas and trying to attract mates, many birds also sing at high speed in more social contexts.
"Our results suggest that birds sing because they feel good, and that singing helps them maintain this positive state."
After discovering that birds associate singing with pleasure, they wanted to find out exactly why – in theory, this was due to the production of opioids in the bird's brain.
Opioids like fentanyl, heroin, and morphine are known to provide pleasure and relieve pain, but animals, including humans, also produce their own natural opioids.
This production of the pleasurable chemical plays a central role in rewarding positive behaviors such as socializing, eating, and mating.
The low dose of fentanyl given to the birds to induce artificial pleasure should reproduce the levels expected when they sing for joy.
The team says this automatically triggered high rates of the type of warbling song seen when the birds are in the flock.
When birds sing, opioids are created in their brains – to prove this, the team, led by biologist Lauren Riters, gave the starlings a drink of fentanyl and then listened to their song.
"Here we showed that opioids cause the singing behavior," Riters said, adding that it also appeared to reduce the birds' stress-related behavior.
They could also show the opposite – by using chemicals to turn off the opioid receptors in the brain, they could reduce how much the birds sing.
The overall results suggest that the presence of herdmates can naturally lead to opioid release in the brains of birds and induce a positive, fearless state.
They also found that singing itself can trigger the same response and that the same findings in the brain of birds could apply to almost all animals.
"If so, it would mean that our studies in songbirds would reveal an ancient, evolutionarily conserved neural circuit that regulates the intrinsically rewarded social behavior of many animals," Riters told Psychology Today.
Discovering an underlying link between socialization and opioid release could help researchers develop therapies for people who are socially withdrawn.
The results were published in the journal Scientific Reports.
BIRDS USE SONG TO COMMUNICATE WITH OTHER BIRDS
Birds use their voices to communicate with other birds.
Sharp melodies are an efficient way to communicate over long distances, especially if you are small and live in dense habitats like rainforests.
Most bird species use special calls to identify themselves and communicate a nearby threat.
Bird singing is a special type of call that is used by many species to help them mate.
Chirping birds is almost entirely a male activity and helps the singer show that he is fit, healthy, and ready to breed.