Deep in the untouched forests of South America live birds whose songs rival the noise of heavy machinery or the front rows of a rock concert. The most striking of them is the bare-necked bellbird: known for its snow-white plumage and the blue-green gradient on its throat, this bird exceeds 130 decibels with its metallic-sounding mating call. That performance makes it a leading candidate for the title of the world's loudest bird.

The mechanism behind these eardrum-rattling sounds was investigated by a team at the University of Massachusetts Amherst. The study succeeded in explaining the anatomical basis of the sound production — but it also raised new questions about the evolutionary story behind the noise.

Body size and beak gape boost the power of the sound

The record was first broken in 2019: the bare-necked bellbird's close relative, the white bellbird, hit a surprising peak that year with a call measured at 125 decibels. New research has now shown that even that threshold can be surpassed.

Led by João Menezes and Jeff Podos, the team compiled sound recordings collected from 123 separate species into a comparison table. The result was clear: there is a direct relationship between sound intensity and anatomy. Birds with larger bodies — and especially with beaks that can open wider — transfer considerably more acoustic energy to their surroundings.

Why did evolution choose such a loud voice?

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The gap between species is striking. The call of the Canada goose reaches 100 decibels — equivalent to a chainsaw — while the starling manages only 70 decibels, about as loud as a dishwasher.

To explain this disparity, the researchers tested a range of hypotheses, including mating displays, habitat density and flight ability. Yet no single evolutionary rule emerged that covers all species. What need drives such enormous acoustic power remains, for now, a question scientists cannot answer.