Some birds are famous for their loud calls, but until recently, nobody could say exactly how loud most birds really are. Researchers at the University of Massachusetts Amherst, in the United States, have now measured the voices of 123 kinds of birds, and before their work, only about 10 of those species had ever been measured at all. Along the way, they found two birds from Brazil that are as loud as a jackhammer, the noisy machine that road workers use to break up concrete. The study was published on September 29 in the journal Evolution.
The reason so little was known is that measuring a bird’s voice is tricky. A call sounds quieter the farther away you are, so you need to know exactly where the bird is. João Menezes, the study’s lead researcher, said that until recently, this kind of measuring was simply not practical outside, in nature. He and his colleague Jeff Podos used laser rangefinders, the same tools golfers use to measure distance, together with sound meters. This let them work out how loud each call would be from one metre (about three feet) away. They recorded birds in Massachusetts and Brazil for more than six years.
Sound is measured in decibels. The quietest bird in the study, a tiny hummingbird called the dusky-throated hermit, reached about 64 decibels, close to a normal conversation. At the other end, the bare-throated bellbird’s loudest call hit almost 131 decibels, and the red-legged seriema reached almost 121. “The nearest comparison in everyday sounds would be a jackhammer,” Menezes said. These two birds now join the white bellbird, also from Brazil, which holds the Guinness World Record for the loudest bird call, as the loudest birds known. All three go above 120 decibels. Podos thinks that is close to the physical limit for a bird, so any loud birds still waiting to be measured are unlikely to be much louder.
The study also found a clear pattern. Bigger birds with wider mouths tend to be louder, because their stronger muscles can push out more air, and a wide-open beak lets more sound escape.
Body size explains how a bird can be so loud, but not why it needs such a big voice. Scientists thought very loud calls helped birds reach each other through thick forest, or attract many partners. That works for the bellbirds, which live in forests, but not for the seriema. It lives in open land, such as pasture, and stays with one partner for the breeding season. So far, nobody knows what its loud call is for.
Bird experts who were not part of the study say the work matters. Elizabeth Derryberry, a bird scientist at Cornell University, said the team is “starting to fill in what’s a pretty large gap in knowledge.” She added that learning more about how these birds behave can help efforts to protect them. Podos called the project “basic, foundational research that no one else has managed to do on this scale.”
Sources: CNN, WBUR, Smithsonian
Some birds are famous for their deafening calls, yet until recently nobody could say with any precision how loud most birds actually are. Researchers at the University of Massachusetts Amherst have now measured the vocal volume of 123 bird species, and before their study, reliable figures existed for only about 10 of them. Along the way, they identified two Brazilian birds whose calls rival a jackhammer, the machine road crews use to break up concrete. The findings were published on September 29 in the journal Evolution.
The gap in knowledge comes down to a practical problem: a call fades quickly with distance, so measuring its true strength means knowing exactly how far away the bird is. João Menezes, the study’s lead author, said that until recently it was simply impractical to take these measurements out in the field. He and fellow biologist Jeff Podos solved the problem with laser rangefinders, the kind golfers use, paired with sound level meters. After correcting for background noise and distance, they calculated how loud each call would be from one metre (about three feet) away. Between December 2018 and January 2025, they recorded birds in Massachusetts and in a range of habitats in Brazil.
The results span an enormous range. The quietest species, a hummingbird called the dusky-throated hermit, reached about 64 decibels, roughly the level of everyday conversation. At the other end of the scale, the bare-throated bellbird averaged 122.4 decibels, with one call peaking at almost 131, while the red-legged seriema reached almost 121. “The nearest comparison in everyday sounds would be a jackhammer,” Menezes said. Both birds now stand alongside the white bellbird, another Brazilian species and the Guinness World Record holder for the loudest bird call, as the loudest birds known, all above 120 decibels. Podos believes that figure is close to the physical limit for a bird, which suggests that no undiscovered species is likely to be dramatically louder.
A clear pattern also emerged. Larger birds with wider mouth openings tended to be the loudest, since bulkier muscles can build up more pressure inside the body and a broad, open beak lets more sound energy escape.
Body size explains how these birds can be so loud, but not why they evolved such powerful voices in the first place. Scientists have long suspected that extremely loud calls evolved to carry through dense forest or to help birds attract several mates, which suits the forest-dwelling bellbirds. The seriema fits neither explanation. It lives in open country such as pasture and is “strictly monogamous,” as Menezes put it, pairing up with a single partner for the breeding season. What the seriema gains from all that volume remains an open question.
Experts who were not involved in the study welcomed the results. Elizabeth Derryberry, an ornithologist at Cornell University, said the team is “starting to fill in what’s a pretty large gap in knowledge,” calling the data “a really useful piece of information from a conservation perspective.” Nathan Senner, an ornithologist at UMass Amherst and the Massachusetts Audubon Society, noted that a sound’s strength, or amplitude, “is so critical to the ability of birds to communicate with each other.” For Podos, the project is “basic, foundational research that no one else has managed to do on this scale.”
Sources: CNN, WBUR, Smithsonian
