Researchers report that they have recorded the bird with the loudest song ever recorded, which lives north of the Amazon.
The researchers involved in the study, published in Current Biology , are biologists Jeff Podos, from the University of Massachusetts Amherst, and Mario Cohn-Haft, from the National Institute for Amazon Research.
Now recognized as the birds with the loudest songs in the world, the so-called bellbirds have a higher sound pressure (125.4 decibels) than the pihas gritantes (116 decibels), another Amazonian species that has now been demoted to second place, say the authors.
Podos says the songs are so deafening that they reach decibel levels equal to the loudest human instruments. They measured the pressure using a new-generation sonometer. These instruments allow you to take calibrated amplitude measurements with very high temporal accuracy, he adds. "This allows us to see how amplitude changes and peaks within individual singing events.
"We've been fortunate enough to see females join males on their display perches. In those cases, we've seen that the males only sing their loudest songs. Not only that, they spin dramatically during those songs so as to blast the final note of the song directly at the females. We'd like to know why females stay so close to males who sing so loudly," Podos says. "Maybe.they are trying to assess the males closely, though at the risk of damaging their hearing aids.
Among other goals, they tried to identify adaptations such as respiratory musculature, head and beak size, and throat shape and how they might influence the birds' unusual aptitude for long-distance song transmission, a topic that has been very poorly studied, Podos says. "We don't know how small animals can make so much noise.We are trulyin the early stages of understanding this biodiversity".
One of the new things the researchers learned is that there seems to be an exchange at work for this behavior - as bellbird and piha songs get louder, they get shorter, they report. That may be because the birds' respiratory systems have a finite ability to control airflow and generate sound.
For Podos, the National Institute of Manaus the largest city in the Amazon, is a global center for the study of biodiversity.
The study's co-author, Mario Cohn-Haft, who grew up in Williamsburg, Massachusetts, is a bird conservationist at the National Institute and a world expert on Amazonian birds and their identifications. Mario has led expeditions for years into remote Amazonian areas to find and characterize bird species, habitats, behavior, and vocalizations, which are still poorly known.
On those previous expeditions, Mario noticed that bellbirds had some interesting anatomical features, including thick, well-developed abdominal muscles and ribs, but science knew almost nothing about this, leading up to the expedition. For Podos, the recent findings provide new information, and an example of the consequences of sexual selection, which drives evolutionof exaggerated features like the high corner.
RELEASE / University of Massachusetts at Amherst via ScienceDaily / DOI :10.1016/j.cub.2019.09.028
