Why can some birds mimic sounds with enough complexity to imitate human speech, while other birds simply chirp?
A new study in the journal PLOS ONE finds that parrots’ ability to learn and imitate new sounds comes from a unique brain region that duplicated some 29 million years ago. Within this region is a pair of nested vocal learning centers that may be the key to parrots' ability to imitate sounds with uncanny accuracy.
Led by neurobiologists at the Duke University Medical Center, the researchers examined brain tissue from a wide range of parrot species capable of vocal learning, including budgies, cockatiels, lovebirds, macaws, and keas. They compared the structure of their brains to the brains of other birds, like songbirds and hummingbirds, which exhibit some signs of vocal learning but can’t imitate voices to the degree a parrot can.
Image Credit:Courtesy of Jonathan E. Lee, Duke University
Parrots’ brains have two structures (see image above) devoted to vocal learning and imitation called a core and a shell, the latter of which is larger in birds known to be better imitators of human language. “Each (vocal learning center) has a core and a shell in the parrot, suggesting that the whole pathway has been duplicated,” study co-author Erich Jarvis, an associate professor of neurobiology at Duke, explains in a press release. The group hypothesizes that birds’ ability to imitate voices and sounds came about through this duplication of pathways in the brain, though they're not quite sure how the duplication might have occurred.
The kea, a relatively ancient parrot species native to New Zealand, also has a crude shell structure, suggesting that the feature dates back to bird species at least 29 million years old. These shell regions have been known to scientists for decades, but it wasn’t clear if they had anything to do with vocal learning.