Vocal repertoire and group-specific signature in the Smooth-billed Ani, Crotophaga ani Linnaeus, 1758 (Cuculiformes, Aves)

Abstract

Vocal plasticity reflects the ability of animals to vary vocalizations according to context (vocal repertoire) as well as to develop vocal convergence (vocal group signature) in the interaction of members in social groups. This feature has been largely reported for oscine, psittacine and trochilid birds, but little has been investigated in birds that present innate vocalization. The smooth-billed ani (Crotophaga ani) is a social bird that lives in groups between two and twenty individuals, and which presents innate vocalization. Here we analyzed the vocal repertoire of this species during group activities, and further investigated the existence of a vocal group signature. The study was conducted in the Southeast of Brazil between May 2017 and April 2018. Two groups of smooth-billed anis were followed, Guararema and Charqueada groups, and their vocalizations were recorded and contextualized as to the performed behavior. The vocal repertoire was analyzed for its composition, context and acoustic variables. The acoustic parameters maximum peak frequency, maximum fundamental frequency, minimum frequency, maximum frequency and duration were analyzed. To verify the vocal signature of the group, we tested whether there was variation in the acoustic parameters between the monitored groups. We recorded ten vocalizations that constituted the vocal repertoire of the Smooth-billed Ani, five of which (“Ahnee”, “Whine”, “Pre-flight”, “Flight” and “Vigil”) were issued by the two groups and five exclusive to the Charqueada group. There were significant differences in the acoustic parameters for “Flight” and “Vigil” vocalizations between the groups, suggesting vocal group signature for these sounds. We established that the Smooth-billed Ani has a diverse vocal repertoire, with variations also occurring between groups of the same population. Moreover, we found evidence of vocal group signature in vocalizations used in the context of cohesion, defense and territory maintenance.

Australian Magpies discriminate between the territorial calls of intra‐ and extra‐group conspecifics

“…The vocal discrimination observed in this study may arise as a result of Western Australian Magpie groups possessing group‐specific vocal signatures, as has been seen in other group‐living species (Radford 2005, Mumm & Knörnschild 2017, Monteiro et al . 2021). Indeed, past research on an eastern subspecies of Australian Magpie identified that individuals within the same group produced similar vocalizations, thus providing a potential mark of group membership (Brown et al .…”

Vocal complexity in a socially complex corvid: gradation, diversity and lack of common call repertoire in male rooks

“…One example is the phenomenon called 'vocal signature' [19][20][21], which does not impact function, but can serve to identify individuals (e.g. in birds [22][23][24][25][26][27]; primates [28][29][30][31][32]; mongoose [33]; cetaceans [34][35][36]), or can signal social group membership [36,37]. Another example are dialects, variations between geographically separate populations [12,38,39].…”