Two South American birds have been identified as contenders for the title of the world's loudest bird, with calls that reach amplitudes comparable to a jackhammer. The bare-throated bellbird and the red-legged seriema both produce songs exceeding 120 decibels, according to a study published Tuesday in the journal Evolution.
Researchers at the University of Massachusetts Amherst measured the vocalizations of 123 bird species in Massachusetts and Brazil between December 2018 and January 2025. The calls of 113 of those species had never been recorded before. The bare-throated bellbird's shout was recorded at 122.4 decibels when measured from a standardized distance of 1 meter, averaged over a 20 millisecond time block. That sound pressure is 800 times that of the quietest species recorded, the dusky-throated hermit hummingbird, which calls at 64.1 decibels.
«The nearest comparison in everyday sounds would be a jackhammer,» said study co-author and evolutionary biologist João C.T. Menezes, who conducted the research as part of his PhD along with his former teacher, biology professor Jeff Podos.
Which bird actually holds the title depends on the criteria used. A bare-throated bellbird achieved the loudest single call, reaching a peak volume of almost 131 decibels across 1 meter. When averaging the noisiest calls made by all birds studied over a 20 millisecond block, the red-legged seriema comes out on top at almost 121 decibels. But when averaging the peak volume reached at any given moment, the white bellbird leads at 127 decibels across six birds. The white bellbird was found in 2019 to screech at up to 125 decibels and was crowned by Guinness World Records as having the loudest bird call.
«It depends on how one defines 'loud,' underscoring the difficulties in measuring loudness,» said Catherine Sheard, an evolutionary biologist and interdisciplinary fellow at the University of Aberdeen in Scotland who was not involved in the study.
Measuring bird calls in the field has been limited by operational challenges. Researchers need to know how far away a bird is when it calls because distance affects perceived loudness. Yet a bird might be heard but not seen, and when it is finally spotted, it may fly away or «stops singing altogether out of shyness,» Menezes said. The authors overcame this by using laser range finders, tools commonly used by golfers to measure distance to the hole, allowing them to measure volume and distance simultaneously.
After correcting for background noise and distance, the researchers compared sound readings with data on body sizes and open beak widths. They found that larger species and those with broader mouth openings tended to sing louder. «Bigger birds have bulkier muscles, which are capable of creating greater internal pressures, which ultimately generate louder sounds,» Menezes said, «and then broader mouths allow more energy to radiate into the environment.»
Yet some birds can sing louder than animals much larger than themselves, such as elephants, lions or bison, indicating another mechanism at play that has yet to be discovered. The researchers also could not conclusively say what environmental and evolutionary factors have led some birds to shout more loudly than others. Bellbirds live in forests and are polyamorous, so researchers predicted they would make louder calls to communicate across dense woodland and to attract multiple mates. However, loud red-legged seriemas are strictly monogamous and typically live in open habitats, so they do not share the same reasons for being loud.
Despite recording the amplitude of many birds' calls, «it's such a tiny fraction still,» Menezes said, adding that «there's so much to answer yet.» Sheard echoed that sentiment. «It doesn't surprise me that even a relatively modest survey of volume has newly identified some very loud birds,» she said. «As fieldworkers continue to collect more data on avian sound, I would predict that even more 'loudest' birds will be identified in the future.»
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