Parrots are so good at repeating human speech that it's easy to forget that, most of the time, they have no idea what they are saying. Now scientists might be on track to explain why they are such accomplished mimics. Compared with other birds that can learn songs, parrots have extra components in the structures in their brains needed for vocalization.
Parrots, along with hummingbirds and songbirds, are vocal learners—they can learn complex songs from their peers. "Quails or chickens, they also produce what are known as innate calls but they don't have what is called vocal learning. They don't need a tutor to teach them that song," said Mukta Chakraborty, a neurobiologist at Duke University and coauthor of the new research published today in PLOS ONE. "The same idea goes for humans as well, they pick up their language from their parents."
But unlike songbirds, parrots can also keep learning calls throughout their lifetime. And they don't just pick up calls from their own species—they also imitate other sounds.
To investigate what sets parrots apart, Chakraborty and her team compared the brains of nine species, among them budgerigars, cockatiels, African Grey parrots and blue and gold macaws.
Like hummingbirds and songbirds, the parrots had seven song nuclei, or brain areas associated with producing song. But in four of these areas, the team discovered a sort of outer ring or "shell" around the core of the song nucleus. And in species known for being superior mimics, such as the macaw and African Grey, the shells were much larger relative to the cores. The researchers call this core-and-shell structure "a song system embedded within a song system."
In the most ancient species of parrot the researchers examined, the kea, the shell structure was more rudimentary. This indicates that parrots have had shells in their song-producing nodes for more than 29 million years, when the kea split off from other parrot lineages.
"Whether the shell is producing or imparting that extra special ability for them to be better imitators, that's the question we are going to try to answer next," Chakraborty said.