Science1 publisher2 min readPublished
Field measurements of 123 bird species tie the loudest calls to big bodies and wide beaks
UMass Amherst biologists measured calls from 123 bird species in the field and found the loudest, above 120 decibels, come from big birds with wide beaks. Their tests of flight ability, forest habitat and mating system as reasons for loudness found no clear pattern.
The Scientist · Science desk
What happened
- The bare-throated bellbird and the red-legged seriema called loudest in the survey, and the authors name both as contenders for the title of world's loudest bird.
- Of the 123 species measured around Amherst, Massachusetts, and across Brazil, 113 had never had their call volume cataloged before.
- The study is by Jeff Podos of UMass Amherst and his former graduate student João C.T. Menezes, and it is published in the journal Evolution.
- Podos found in 2019 that the Amazon's white bellbird had the loudest known bird call, a claim Guinness World Records later confirmed.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- constraint Arguments that habitat, flight ability or mating system shape how loud a bird gets remain untested hypotheses; by Menezes's account, testing them will take far more species than 123.
- capability Measuring volume at a known distance outdoors lets surveys include species that would be impractical to capture and test in a lab, particularly across countries.
- constraint Because loudness falls with distance, any contest for the loudest-bird title turns on readings taken at a stated distance, and a peak decibel figure alone cannot settle it.
A 58 dB spread between the quietest and loudest calls in the survey covers more ground than the number suggests [5]. Decibels are logarithmic, so that gap is roughly 800 times the sound pressure [1]. The quiet end was a hummingbird at 64 dB, about the level of ordinary conversation [5]. The stated range puts the loudest peaks near 122 dB [2].
Getting reliable numbers outdoors was the hard part. Loudness depends on distance: a scream that is ear-splitting up close might barely register a few hundred meters away [11]. Catching birds and running controlled tests on them is impractical when the work spans countries and large numbers of birds [12]. "Figuring out how loud a bird call is should be pretty easy in the lab," Menezes said. "But until very recently, it has been very challenging to do in the field, and there's very little data to draw on." [10]
The workaround came from golf and workplace safety. Laser rangefinders built for golfers and high-resolution portable sound meters built for safety monitoring let the pair log distance and volume at the same time [4]. "You have to get your boots on the ground," Podos said [13].
On anatomy, a pattern held. The loudest birds were typically bigger, with bulky muscles and wider beak openings [6]. The thing this doesn't tell you is cause. The survey links field measurements of sound to body features across species, and the account presents the muscle explanation as a possibility: the bulk may allow greater air compression [6].
The ecological predictions did not hold up. Menezes and Podos had expected the loudest callers to be weak flyers making up for limited mobility, residents of dense forest where birds cannot see each other, and polygamous species whose mating calls would reach more mates [7]. The data supported no clear, broad pattern of that kind [7]. A null result across 123 species means this sample could not detect such effects [3], and Menezes treats it that way. "We now know some of the hows," Menezes said. "Bigger bodies and wider beaks, but we've yet to discover the whys, and we probably need much more data from many more species to be able to tease out what's going on on the ecological and evolutionary front." [8]
I think the anatomy result is solid as a description and the ecology result is an open question, which is how the authors frame it too [8]. The phys.org account does not give the white bellbird's 2019 figure or the distance at which the new peaks were measured [9].
What to watch
- A larger follow-up sample from Podos and Menezes testing whether flight ability, forest habitat or polygamy tracks call volume once many more species are included.
- A distance-matched comparison of the bare-throated bellbird and red-legged seriema against the white bellbird's 2019 figure, and any Guinness World Records review of it.