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Anselmo D’affonseca

A white bird that lives on mountains deep in the Brazilian Amazon rainforest has the loudest voice of any bird species recorded so far.

Both songs of the white bellbird (Procnias albus) are loud but one is extremely so – at an average of 116 decibels at a distance of one metre, it is on a par with a pile-driver and beats all previously documented birds.

“It’s really, really distinctive and it’s unusual because it’s very simple. It’s one loud note, like a horn,” says Jeffrey Podos of the University of Massachusetts.

It’s not just the volume that is unusual, but the fact the males sing so loudly at very close distance to females – we’re not sure why, says Podos.

Most animals that make very loud sounds – such as howler monkeys – are trying to communicate over long distances. There is also that for some birds, quieter songs during courtship makes males more likely to be chosen by females.

Joseph Tobias at Imperial College London speculates that the close proximity suggests the loudness of the song is a sexual signal.

“If females detect the loudest males from longer range, and find the loudest males most attractive at close range, then sexual selection would drive the evolution of extremely loud songs, up against the limits of physical performance constraints,” he says.

There are several reasons their voice is so loud. The song is very simple, with just one frequency and no flourishes, making it easier to boost the volume. Dissections have shown that, unlike most birds, the species has great abs, with stomach muscles that are thickened and defined.

The loudness also seems to be a byproduct of the ecological niche they have evolved to occupy: their beaks open remarkably wide, helping them to catch their entirely fruit-based diet, as well as make a loud song.

There is almost certainly a louder bird out there, such as a crane or swan, says Podos, as so few species have had their songs properly measured. “That doesn’t diminish how remarkable the bellbirds are because they’re much, much smaller,” he says.