A team led by University of Utah biologist Franz Goller studied how brown-headed cowbirds (Molothrus ater) produce a distinctive watery timbre in their songs. The study, published in Current Biology, lists coauthors who bring expertise in neuroscience and physics. Goller, a professor emeritus of biology, has long studied bird vocalizations with funding from the National Institutes of Health.
The researchers showed that sound is produced in the syrinx, a vocal organ with two separate sound sources, one on the left and one on the right. Cowbirds make the gurgling, bubbling quality by rapidly switching between the two sides. The left vocal folds are much larger, and some parts of the notes are alternating contributions from left and right. The birds also control breathing: they briefly hold breath to build pressure and then release it quickly, producing a splash-like burst with a rapid attack and slower decay. A second, more audible sound follows shortly when an air bubble implodes, and droplet size affects pitch.
The team raised captive starling hatchlings alongside cowbirds. The starlings learned to reproduce the cowbird vocalizations and used similar breathing and valve control. Coauthor Brenton Cooper noted that birds are vocal learners and that such studies help explain human speech and language.
Difficult words
- syrinx — bird vocal organ where sound is produced
- timbre — quality of sound that makes tone different
- vocal fold — thin tissue in vocal organ that vibratesvocal folds
- implode — to burst inward quickly with loud effectimplodes
- hatchling — a very young bird recently out of egghatchlings
- vocal learner — an animal that learns sounds from othersvocal learners
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- Why did the researchers raise starlings alongside cowbirds to study vocal learning?
- How could findings about bird breathing and valve control help explain human speech?
- Which detail in the study did you find most interesting, and why?
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