Study identifies world's loudest birds, reveals how but not why extreme volume evolved

A jackhammer produces roughly 130 decibels. A chainsaw, around 120. And somewhere in the Atlantic Forest of Brazil, a bare-throated bellbird opens its throat and matches that roar—a sound so extreme that for decades, no one had bothered to measure it properly. The problem was simple but stubborn: sound fades with distance. A call that shatters a microphone held inches away might barely whisper at fifty feet. For biologists scattered across continents, trying to compare which birds actually shouted loudest, that basic physics made the question nearly impossible to answer with any rigor.

Jeff Podos, a biologist at the University of Massachusetts Amherst, decided to solve it the way field scientists have always solved hard problems—by going outside and measuring things carefully. He and his former graduate student João C.T. Menezes carried two pieces of equipment into the field: a laser rangefinder borrowed from golf course design, and a high-resolution portable sound meter. The rangefinder told them exactly how far each bird was when it called. The sound meter told them how loud that call actually was. Together, the devices gave them something ornithologists had never had before at scale: reliable amplitude data from wild birds, measured in their actual habitats.

Between the forests around Amherst, Massachusetts, and across Brazil, they measured 123 species. Of those, 113 had never been cataloged for call volume before. The range they found was staggering: fifty-eight decibels separated the quietest from the loudest. A hummingbird's call registered around sixty-four decibels—roughly the volume of normal conversation. At the other end, bare-throated bellbirds and red-legged seriemas climbed above 120 peak decibels. Podos had encountered such extremes before. In 2019, he reported that the Amazon's white bellbird produced what was then recognized as the world's loudest known bird call. Guinness World Records took notice. But the real question was never about records. It was about why.

When Podos and Menezes compared the bodies of their birds to their measured calls, some patterns emerged. Larger birds tended to be louder—their bigger muscles could compress and force out more air. Wider beak openings correlated with louder calls too, much as the broad bell of a trumpet projects sound farther than a narrow opening would. These were the mechanics of extreme volume, the physical "how" of it. But the "why" remained elusive. The researchers had expected to find clear ecological reasons for such extreme loudness. Birds that were weak flyers might need to communicate across distance without moving. Dense forest dwellers might rely on sound because visual signals couldn't penetrate the vegetation. Males practicing polygamy might benefit from calls that carried farther, reaching more potential mates. Each hypothesis made intuitive sense.

None of them held up. The data refused to show a clear, broad pattern linking loudness to any of those ecological circumstances. Body size and beak width explained some of the variation in call volume. But the deeper evolutionary reasons why certain birds became exceptionally loud—why they invested so much energy in such extreme acoustic power—remained mysterious. "We now know some of the hows," Menezes said. "Bigger bodies and wider beaks. But we've yet to discover the whys, and we probably need much more data from many more species to be able to tease out what's going on the ecological and evolutionary front."

The study, published in Evolution in late September 2026, represents the most comprehensive wild measurement of bird call amplitude ever assembled. It is also, in a sense, an invitation. Podos and Menezes have established the method. They have shown that it works. They have created a foundation of reliable data that didn't exist before. But the real work—understanding not just how birds make these extraordinary sounds, but why evolution favored such extreme volume in some species and not others—remains ahead of them. Back in the field, that means more birds to find, more distances to measure, more calls to catch at exactly the right moment. The rangefinder and sound meter are ready. The questions are still waiting.