UMass biologists discover what may be the world's loudest birds

Biologists at the University of Massachusetts Amherst have discovered what may be the world’s loudest birds, all living in Brazil. But exactly why these birds evolved to be so noisy remains a mystery.

The finding was published Tuesday in the journal Evolution.

This is not the first time UMass biologist Jeff Podos has discovered the world’s loudest bird. In 2019, he clocked the white bellbird at 125 decibels — louder than a jackhammer. The bird, which sounds like a smoke detector that needs a new battery and attracts mates by screaming in their faces, has its own entry in the Guinness World Records.

For the current study, Podos, working with his recently-graduated Ph.D student João Menezes, collected amplitude data on 123 bird species in Brazil and Massachusetts. The team found two more birds that broke 120 decibels: the bare-throated bellbird and the red-legged seriema.

The bare-throated bellbird has a piercing squawk that’s similar to the white bellbird; the red-legged seriema sounds sort of like an angry gull. The seriemas sing in duets, much like an older couple squabbling in Walmart.

All three birds have some common physical features: namely, wide beak openings and big bodies with bulky muscles. Podos said 120 decibels seems to be around the physical limit for birds; so while there are undoubtedly loud birds outside Brazil, they are unlikely to be much louder than these.

All three birds could be considered the loudest, depending on the exact measurement criteria. (Like, should the loudest individual squawker take the crown, or should it go to the loudest average among several birds?) But Podos said that for scientists, the winner is beside the point.

“We're not actually super interested in the race to say which is the loudest bird, because that's not really a biological question,” said Podos. “What's really interesting is: there are some species of animals that have evolved to be super loud, and we just wonder why that is.”

The scientists had suspected that the birds blast their sounds either to communicate through dense jungle, like howler monkeys, or to attract as many mates as possible. But the red-legged seriema confounded their theories.

“The seriema is the opposite of those two things,” said Menezes. “It's a super open-habitat bird, like pasture, and it's strictly monogamous. So it forms a pair for the breeding season, and that’s it.”

So, it’s still a mystery why these birds spend so much energy screaming at each other. But Cornell ornithologist Elizabeth Derryberry said the research is an important step forward in our understanding of bird evolution. Even though scientists have been studying birdsong for decades, it’s only recently that technology has allowed easy, accurate measurements of amplitude.

“It’s exciting to see work like this because they're starting to fill in what's a pretty large gap in knowledge,” said Derryberry, who directs Cornell’s  Macaulay Library of Natural Sounds and was not involved with the research.

She said if scientists better understand how the birds evolve and behave, it could lead to better protections.  “It's a really useful piece of information from a conservation perspective,” she said.

Mass Audubon ornithologist  Nathan Senner called the findings “remarkable.”

“Amplitude is so critical to the ability of birds to communicate with each other, that it is really important for us to understand exactly how that might be able to change,” said Senner, an assistant professor of Environmental Conservation at Umass Amherst who was not involved in the research. “How they evolve is really fundamental to our understanding of how they might continue to evolve as our world changes.”