Sleepy Birds Are Lousy Singers, Study Finds

Late at night in Auckland, New Zealand, researchers Juliane Gaviraghi Mussoi and Kristal Cain shuffled quietly around a dimly lit room with 13 caged Common Mynas. Everyone was sleepy—especially the birds. Over and over their eyelids would droop as they nestled their beaks under their wings, settling into stillness. But each time the birds began to drift off, the humans intervened: They walked more energetically about the room, tapped lightly on the enclosures, and gently nudged the sleepiest birds awake. 

For the sake of science, birds and biologists alike would be pulling an all-nighter. 

The next day, the songbirds seemed off: They were quieter than usual, and when they did sing, they performed simpler renditions of their typical tunes. It turns out that, like us, Common Mynas aren’t quite themselves after a night of bad sleep.

The discovery, detailed in a new study in Proceedings of the Royal Society B, suggests that persistent nighttime disturbances such as noise or light pollution could affect the daytime vocals of birds in the wild, which in turn could make them less fit for reproduction and survival. 

Common Mynas—native to southern Asia but prolific and invasive in New Zealand and many parts of the world, including southern Florida—are known to thrive in urban environments. If late-night ruckus takes a toll on even these city dwellers, it’s likely that more sensitive native species are vulnerable, too, says Cain, an animal behaviorist at the University of Auckland.

Birds vocalize for all kinds of reasons, says Mussoi, a behavioral ecologist at the University of Waikato. They use long, often melodic songs to attract mates and establish territory. Their calls, on the other hand, are shorter and less musical, and used to signal danger, draw attention to food, and socialize.

To study how a lack of rest affects these vocalizations, Mussoi, Cain, and their research team deprived the Common Mynas of sleep three separate times. One night, the birds were kept awake for a full 12 hours. The following day, their time spent singing decreased by an average of 89 percent, compared with after a full night’s rest. The birds were also 52 percent less physically active than usual, spending less time moving around their cages and more time snoozing. “These birds are missing out on critical communication periods because they’re napping,” Mussoi says. 

The other nights, the birds were kept awake for six hours, either during the first chunk of the night or the second, and their songs still suffered: They sang 32 percent less than normal after sleeping the first half of the night and 95 percent less after sleeping the second half.

The tired birds not only sang less, but their songs were noticeably less intricate after each night they were kept awake. “If birds are too tired to vocalize or sing less complex songs, it could really disrupt their ability to find a good mate,” Mussoi says. Sleep deprivation may also leave birds more vulnerable to daytime predators, Mussoi says. “If it’s a long-term issue, there could be fitness consequences.”

Unlike their songs, the Common Mynas’ calls remained surprisingly steady. Cain suspects that this is because, after a rough night, the birds had a lot to chitchat about. “Birds use calls as a means of checking in on one another, and they’d had quite an unusual night,” she says. “Imagine you and your family were kept up all night by fire alarms or something. There’d be a lot of, ‘Are you okay?’ and ‘How’s everyone doing?’” 

The researchers note that their findings may lend insight into human speech and early childhood development. Like humans, young birds learn how to vocalize by listening to the adults around them. They memorize song and call patterns via brain pathways similar to those in people and rely on periods of rapid eye movement sleep to retain those memories. Studying how poor sleep affects birds could help researchers better understand how speech develops in children with chronic sleep troubles, Mussoi and Cain say.

The Common Mynas’ sluggishness also hints at how urbanization may be chronically interrupting birds’ sleep and changing their behavior. If disturbances like the researchers’ movements were enough to keep the study’s birds awake, car horns, bright street lamps, or late-night concerts likely do the same for those in the real world. To shed further light on those impacts, Cain and Mussoi say they aim to soon publish the results from follow-up experiments using recordings of Auckland’s nighttime sounds.

Relatable as the drowsy mynas may be, not everyone empathizes with the birds. “I’ve noticed a lot of Facebook comments saying things like, ‘This is an awful species. Who the hell cares?’” Cain says. One person even asked Mussoi if people could use bright lights and loud sounds to try and drive away the birds. But the researchers say that the Common Mynas serve as an easy stand-in for songbirds in general. “You can hate Mynas and still care about these results,” Cain says. In fact, Mussoi and Cain were part of a similar study in 2022 that found poorer cognitive performance in Australian Magpies after they were deprived of sleep.

To help birds get better sleep and sing their best songs, people should draw their curtains at night when they have house lights on and try to keep noise after hours to a minimum, says Jennifer Phillips, a wildlife ecologist at Washington State University who was not part of the study. Some research has also shown that cold, white light disrupts birds’ sleep more than warm, yellow light, so swapping out those outdoor bulbs—and turning them off when they’re unnecessary—may help, too. 

“We humans get cranky and usually have bad days if we don’t get enough sleep,” Phillips says. “Well, so do birds and other animals. And if we want to conserve wildlife we need to think about how our activities are potentially messing with their rest.”