Shared calls in repertoires of two locally distant gray parrots (Psittacus erithacus)

Parrots belong to the handful of animal species capable of vocal production learning. They are considered to be open-ended learners with complex and variable vocalizations. It is not known, however, to what extent their repertoires are shared among individuals within a group or between vocally isolated individuals or groups. In study 1, we mapped the repertoire of four captive African gray parrots (Psittacus erithacus) using a combination of three acoustic analyses. In study 2, we compared the repertoire of two female African gray parrots from two different laboratories who had never been in vocal contact with each other or any member of the other parrot's social group. Results of study 1 showed a relatively large agreement between all three methods used to analyze the vocalizations. Almost three quarters (72.8%) of categories determined by visual-acoustic analysis were confirmed by at least one of the two computer-aided methods used, i.e., by spectrographic cross-correlation and/or a multiparametric statistical method. In study 2, we found a relatively large proportion of calls shared between the repertoires of the two gray parrot subjects. Over half and over a fourth of calls produced by parrots with the smaller and the larger repertoire, respectively, were shared between the two. No previous study identified such a large proportion of intergroup shared calls within this parrot species. It seems that some calls tend to reappear in vocally isolated groups based on inherited predispositions, similarly as has been documented in songbirds.