The fascinating ability of parrots to copy new sounds and human speech is far more than just a highly amusing party trick; such vocal learning is rare in the animal kingdom, and only two other avian groups – hummingbirds and songbirds – share these skills.

Some bird species are better than others at playing the imitation game, although why this is has been difficult to determine. But scientists are slowly starting to piece together this puzzle, and new research has identified structural differences in parrot brains that may underlie their unrivaled noise-mimicking talents.

Although this is not the first study to highlight distinctions between the brains of various bird species that display different degrees of vocal learning, earlier work identified differences in the size of certain regions and offered little further explanation. Additionally, the only parrot species whose brain had been probed extensively for potential mechanisms underlying this ability was the budgerigar. The latest research, published in PLOS ONE, offered a more detailed analysis, examining the brain tissue of eight further parrot species, including the African Grey parrot, cockatiels and lovebirds.

For the study, researchers from Duke University set out to investigate how patterns of gene expression varied across the brains of different parrot species, comparing results with those obtained for the other vocal learning groups, songbirds and hummingbirds. More specifically, they were interested in the genes that are active in the vocal learning regions in the brains of humans and song-learning birds.  

This led to the identification of key structural differences between parrots and the other vocal learning bird groups. All of these birds possess defined vocal learning centers, called cores, but parrots have another structure surrounding this region. This outer area, or shell, also seems to play a role in the vocal learning process. Interestingly, the scientists found that the shell was enlarged in those that are best at imitating human speech sounds.

This finding is particularly important because some earlier work had suggested that the shell had no role in the vocal learning process. Adding to the confusion, another study proposed that the shell and core were not actually distinct structures, and instead one large brain region. But this view is outdated, and the fact that such similar neighboring structures are both involved in vocal learning suggests that a duplication event may have taken place in the brain.

“How can you get a mirrored song system surrounding another one?” study author Erich Jarvis asked in a statement. “Each [vocal learning center] has a core and a shell in the parrot, suggesting that the whole pathway has been duplicated.”

Something else that has piqued the interest of researchers is the location of these vocal learning regions, which are among areas involved in the control of movement. Although purely speculation at this stage, it’s possible that this is the reason why some parrots can also dance along to music.

As of now, it remains unclear as to whether the shells are responsible for the parrots’ superior ability to copy human speech, or which particular genes are important for this. Further genetic analysis is therefore required to shed light on these grey areas.