The loudest bird calls ever recorded come from male Amazonian bellbirds, which blast their 116-decibel one-note song directly at unflinching females as part of mating rituals, scientists have discovered.
The recordings were taken in the mountains of the northern Amazon, with researchers saying the amplitude they measured was three times that of screaming pihas, another Amazonian species now demoted to the second-loudest bird ever documented.
In comparison, a 1972 gig by rock band Deep Purple earned the group the accolade of the loudest on earth in the Guinness Book of Records by hitting 117 decibels at the London Rainbow Theatre. Three fans fell unconscious during the show.
The researchers said it was difficult to describe how loud the bellbird’s call was because it is hard to compare sounds from different distances. But the calls are so noisy that scientists are intrigued about how white bellbird females listen at close range without damaging their hearing.
Biologist Jeff Podos at the University of Massachusetts Amherst, who studied the bellbirds alongside Mario Cohn-Haft from the Instituto Nacional de Pesquisas da Amazonia in Brazil, said he believed the females could be risking their hearing to size-up potential mates.
He said: “We were lucky enough to see females join males on their display perches. In these cases, we saw that the males sing only their loudest songs. Not only that, they swivel dramatically during these songs, so as to blast the song’s final note directly at the females.
“We would love to know why females willingly stay so close to males as they sing so loudly. Maybe they are trying to assess males up close, though at the risk of some damage to their hearing systems.”
Bellbirds weigh just half a pound (250g), but despite their diminutive size their calls are far louder than much larger animals, including bison and howler monkeys, according to Dr Podos.
However, the birds still have some way to go to compete with the loudest recorded animal of all – the sperm whale. Sperm whales produce clicks which reach up to 230db and can be measured 500 miles away.
Deep Purple’s 1970s record has also since been broken, with the band Kiss hitting 139db during a 2009 concert in Ottowa, Canada – considerably louder than a bellbird’s call.
To record the bellbirds, the team used high-quality sound recorders plus special sound-level meters and high-speed video to slow the action enough for study.
They also studied the birds’ particular adaptations, such as breathing musculature, head and beak size, and the shape of their throats, and looked at how these may influence the unusual aptitude the birds have for long-distance song transmission – a topic which has been very poorly studied, according to Dr Podos.
“We don’t know how small animals manage to get so loud. We are truly at the early stages of understanding this biodiversity,” he said.
One of the new things the researchers learned is that there seems to be a trade-off at work for this behaviour – as bellbird and piha songs get louder, they also get shorter. This may be because the birds’ respiratory systems have a finite ability to control airflow and generate sound.
The study has been published in the journal Current Biology.