Now recognized as the loudest in the world, bellbird calls have a sound pressure about three times that of screaming pihas, another Amazon species now demoted to the second loudest bird singer documented, the authors say.
University of MA at Amherst, Brazilian institute researchers record top avian noisemaker. Details are in the latest Current Biology. These instruments allow one to take calibrated measures of amplitude with very high temporal precision.
Many male birds have elaborate ways to attract mates.
But the calls are so loud, the researchers wonder how white bellbird females listen at close range without damaging their hearing.
In the mountainous northern Amazon, a tiny white-plumed suitor turns to face his would-be paramour and belts out a deafening, klaxon-like call, reaching decibel levels equal to a pile driver.
The pair used high-quality sound recorders and high-speed video to slow the action enough to study how the bird uses its anatomy to achieve such levels of noise - louder than much larger howler monkeys or bison, but probably not as loud as lions, elephants or whales.
"Calls of howler monkeys and bison are well studied and quite loud, but not almost as loud as the impressive bellbirds, who weigh about half a pound (1/4 kg) compared to the larger mammals", Dr. Podos said. A male only prepares to sing when the female sidles up next to him and stays there.
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Professor Podos said he was lucky enough to witness females join males on their perches as they sang.
"He sings the first note facing away, and then he does this dramatic, nearly theatrical swivel, where he swings around with his feet wide open and his wattle is kind of flailing around", he said.
He said that he noticed that the male sing only their loudest songs. "If she didn't know any better she'd get it in the face".
"For me, it defines the forest where we work", he says. His co-author, Cohn-Haft, who grew up in Williamsburg, Mass., not far from the UMass Amherst campus, is curator of birds at the national institute and a world expert on Amazonian birds and their identification. He had shot a bellbird, and when he opened it up, he was impressed by its hefty, well-defined abdominal muscles - very unusual for a bird.
Standing beside a siren clocks in at 120 decibels, and repeated or routine exposure to sounds that loud can cause pain and ear injury, according to the Centers for Disease Control and Prevention.
While the researchers were studying the white bellbird, in fact, a farmer set fire to a field below the mountain, and the flames spread partway up the mountain before being extinguished.
Podos said he hopes to study the three other species of bellbirds and better understand what the birds do to help them be successful in mating. "If sexual selection keeps pushing the song to be louder and louder, it's going to become shorter and shorter", said Podos.