A duo of ornithologists from the United States and Brazil has recorded the loudest bird song (up to 125.4 db) ever documented, made by males of the white bellbird (Procnias albus); the bellbird songs have a sound pressure about 3 times that of the screaming piha (Lipaugus vociferans), an Amazon bird species now demoted to the second loudest bird singer documented.
The white bellbird is a species of bird in the family Cotingidae (cotingas).
It occurs in the Guianas, with small numbers in Venezuela and the Brazilian state of Pará.
“The bellbird songs are so deafening they reach decibel levels equal to the loudest human instruments,” said Dr. Jeff Podos, an expert in bioacoustics at the University of Massachusetts Amherst.
“We measured pressure using a new generation sound level meter. These instruments allow one to take calibrated measures of amplitude with very high temporal precision. This allows us to see how amplitude changes and peaks within individual singing events.”
Dr. Podos and his colleague, Dr. Mario Cohn-Haft of the Instituto Nacional de Pesquisas da Amazônia, said it’s actually hard to describe how loud the bellbird’s call is, because it’s difficult to compare sounds from different distances.
But the calls are so loud, the researchers wonder how white bellbird females listen at close range without damaging their hearing.
“Calls of howler monkeys and bison are well studied and quite loud, but not nearly as loud as the impressive bellbirds, who weigh about half a pound (1/4 kg) compared to the larger mammals,” Dr. Podos 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.”
The team used high-quality sound recorders plus special sound-level meters and high-speed video to slow the action enough for study.
Among other goals, they tried to identify adaptations such as breathing musculature, head and beak size, the shape of the throat and how these may influence the unusual aptitude the birds have for long-distance song transmission, a topic that has been very poorly studied.
“We don’t know how small animals manage to get so loud. We are truly at the early stages of understanding this biodiversity,” Dr. Podos said.
One of the new things the researchers learned is that there seems to be a trade-off at work for this behavior — as bellbird and piha songs get louder, they get shorter.
“This may be because the birds’ respiratory systems have a finite ability to control airflow and generate sound,” they said.
The team’s paper was published in the October 21, 2019 issue of the journal Current Biology.
Jeffrey Podos Mario Cohn-Haft. 2019. Extremely loud mating songs at close range in white bellbirds. Current Biology 29 (20): 1068-1069; doi: 10.1016/j.cub.2019.09.028