The bare-throated bellbird has a voice that is almost impossible to ignore.
The snow-white male, a sturdy South American bird with a broad bill and a distinctive blue-green patch on its throat, can produce an explosive metallic call reaching more than 130 decibels.
That’s louder than a jackhammer and powerful enough to make this forest-dwelling bird a serious contender for the title of the world’s loudest bird.
Now, researchers believe they may have uncovered part of the secret behind these astonishing vocal abilities.
A new study suggests that birds with larger bodies and, in particular, wider beaks tend to produce louder calls. Behavioral ecologists João Menezes and Jeff Podos of the University of Massachusetts Amherst reported the findings in Evolution.
But understanding why some birds evolved such extreme volume is much more complicated.
The researchers examined several possible explanations, including mating behavior, habitat density and flight ability. None of these factors, however, provided a consistent answer across different bird species.
“We weren’t able to find an overarching pattern that applies to birds in general,” Menezes said.
The investigation builds on research that began several years ago. In 2019, Podos and a colleague identified the white bellbird, an Amazonian relative of the bare-throated bellbird, as a remarkable vocal powerhouse.
At the time, the white bellbird’s mating call reached about 125 decibels, making it the loudest bird call ever measured.
That discovery raised a bigger question: What allows certain birds to produce sounds that are so much louder than those of their relatives?
The new research suggests that part of the answer may lie in their anatomy.
Larger birds generally produced louder calls, while birds with wider beaks also tended to reach greater volumes.
The connection makes biological sense. Bigger birds can potentially generate greater respiratory pressure and airflow, while the shape and size of a bird’s beak can influence how efficiently sound escapes from the body.
“With its large body and wide-gaped bill, the bare-throated bellbird has the anatomical hardware to unleash a record-setting call,” Menezes said.
To investigate bird vocalizations more broadly, Podos spent years recording birds in forests, wetlands and open areas around his home in western Massachusetts. Using professional sound-measuring equipment and a laser rangefinder, he recorded species ranging from small songbirds to much louder birds.
Menezes later expanded the project across Brazil, recording birds in environments ranging from the Atlantic Forest near São Paulo to mountainous areas around Rio de Janeiro.
The recordings captured an enormous variety of sounds — from the quiet calls of hummingbirds to the piercing cries of larger grassland birds.
Together, the researchers assembled vocalization data from 123 species, creating what they describe as the largest dataset of its kind so far.
The results revealed a clear relationship between body size, beak width and vocal volume.
Still, the biggest mystery remains unsolved.
Scientists now have a better understanding of some of the physical features that help birds become exceptionally loud. But why evolution favored such extreme vocal power in certain species is still unclear.
For now, the world’s loudest bird may have to keep screaming while researchers continue searching for the evolutionary reason behind its extraordinary voice.