Unlike other animals, according to this NPR article, parrots and elephants are vocal mimics and can imitate sounds. Dancing, then, could be a byproduct of the ability to learn and imitate vocally.
Two papers in today's online Current Biology discuss the dancing parrot:
One reports on "experimental evidence for synchronization to a beat in a sulphur-crested cockatoo (Cacatua galerita eleonora). By manipulating the tempo of a musical excerpt across a wide range, we show that the animal spontaneously adjusts the tempo of its rhythmic movements to stay synchronized with the beat. These findings indicate that synchronization to a musical beat is not uniquely human and suggest that animal models can provide insights into the neurobiology and evolution of human music."
The fourth author, Irena Schulz, runs the bird shelter Bird Lovers Only Rescue Service in Indiana and put a video of Snowball the parrot dancing to the Backstreet Boys on YouTube a few years ago. Someone sent the video to neurobiologist Aniruddh Patel, who is the lead author on the article.
The second article concludes that entrainment, or the aligning of movement to an external auditory pulse, "is not unique to humans and that the distribution of entrainment across species supports the hypothesis that entrainment evolved as a by-product of selection for vocal mimicry."
The idea inspired an evolutionary biologist in Scotland, who mentioned a few experimental possibilities in the NPR article. What genes are turned on while a bird is dancing? What genes are turned on by listening to a beat, versus listening to sounds that don't have a beat? And what would happen if a bird never heard any music for the first few years of its life? Could it still dance later on?
Check out the YouTube video here. Here's one of Snowball dancing to Queen.