Artoo-Detoo: What imitating a Star Wars droid reveals on allospecific vocal imitation in parrots and starlings

Vocal production learning is a widespread and remarkable phenomenon. However, the underlying mechanisms of allospecific vocal imitation are poorly understood. Parrots and corvids are well known for their imitation abilities, but imitation accuracy has not yet been studied across species in a comparative context. We compared imitation accuracy between nine parrot species and European starlings based on imitation of monophonic and multiphonic sounds, produced by the Star Wars droid R2-D2. Our results show that starlings were better at imitating multiphonic sounds than parrots. However, no difference in imitation accuracy was found between parrots and starlings when imitating monophonic sounds. The differences in imitating accuracy are likely based on a physiological difference in syrinx anatomy, rather than on perceptual or cognitive differences between starlings and parrots. Between our nine tested parrot species, we found that parrots with larger brains (e.g., African greys and amazon parrots) were less accurate at imitating monophonic sounds than smaller brained budgerigars and cockatiels. The use of citizen science in our study shows the great potential this has to expand data collection beyond traditional studies. These findings contribute to a deeper understanding of the evolution of communication complexity in vocal learners. Significance StatementVocal imitation is a hallmark of complex communication in animals, yet the mechanisms driving species differences remain poorly understood. By comparing vocal imitation across nine parrot species and European starlings, we demonstrate, for the first time, that differences in syrinx anatomy, rather than cognitive or perceptual capacities, underlie species-specific variation in imitation accuracy. Contrary to traditional expectations, smaller-brained parrots outperformed larger-brained species in monophonic sound imitation. These findings challenge assumptions that brain size is directly linked to imitation accuracy and offer insights into the evolution of complex communication. We used citizen science to create a uniquely large dataset of species imitating the same source, demonstrating the powerful potential of this approach to broaden research in comparative cognition and vocal learning.