Friend or foe? Social system influences the allocation of signals across functional categories in the repertoires of the New World jays

Many factors could influence repertoire size and function. Here, we provide a review of the descriptions of vocal repertoires of New World jays and a unifying terminology for function of their vocalizations. We summarized 19 different functional types of vocal behaviour shared by at least two species, for review purposes. Comparing the 14 studied species, we also classified vocalizations into four major classes defined a priori: ‘Social Integration’, ‘Conflict Resolution’, ‘Predator-related’, and ‘Breeding’. Cooperative breeding, as well as group size, are related not only to repertoire size, but to how species allocate their vocalizations into functional classes. We discuss the tendencies of Conflict Resolution and Social Integration and the possibility of the existence and implications of a trade-off between those functional classes. We identified gaps in the current knowledge on vocalizations of the studied species, and emphasize the importance of empiric evidence of vocalization function in the New World jays.