Perceptual mechanism for vocal individual recognition in jungle crows (Corvus macrorhynchos): contact call signature and discrimination

Abstract

In long-range fission-fusion complex societies, individuals are often recognized by audiovocal signals because of long-range propagation. The signature voice system is a well-known mechanism involving both acoustic individuality of a certain call type and discrimination ability. Previous studies on vocal individual recognition of birds have emphasized its involvement in breeding contexts such as mate, parent and offspring, and territorial-neighbour recognition. However, there has been less focus on the recognition of non-breeding flock members despite the socio-ecological demand of such ability in the complex social lives of highly social birds including corvids. Here we report a signature voice system in jungle crows by showing both acoustic individuality of contact calls and discrimination ability. We first performed a discriminant functional analysis on contact ka calls of five crows to examine their discriminatory potential and demonstrate inter-individual distinctions. We next used an operant conditioning to verify the perceptual ability to discriminate non-breeding familiar conspecifics based on ka calls. Four of the five crows successfully transferred discrimination of individual calls to the novel ka calls. Our results provide the first evidence of a signature voice system as a perceptual mechanism for individual recognition of familiar individuals in non-breeding flocks of a highly social crow.

Individual recognition of opposite sex vocalizations in the zebra finch

“…This delay is roughly similar to the mean latency of calls used as replies and double the length of stack calls 10 ; therefore, this response gap can be biologically relevant and directly used within a communicating group. Individual vocal recognition using contact calls has rarely been investigated in Passeriformes although different functions have been proposed: for example, Large-billed Crows ( Corvus macrorhynchos ) can recognize strangers’ loud calls 23 , Long-tailed bushtits ( Aegithalos caudatus ) kin’s contact calls 6 , Chestnut-crowned Babblers ( Pomatostomus ruficeps ) group members’ contact calls 24 and Silvereye ( Zosterops lateralis ) mates’ calls 25 . However, in most of the studies it was unclear whether these calls were learned and a large proportion of the typical repertoire remained untested.…”

Individual vocal recognition across taxa: a review of the literature and a look into the future

“…Like in go no-go experiments, the individuals are trained to discriminate between specific known categories of stimuli with training data by rewarding the individual for choosing the correct button in response to a stimulus and punishing an incorrect response. Once the subjects reach a certain proficiency with the training stimuli, then they are tested using the same paradigm with the new test stimuli [24,30]. Habituation/dishabituation: These experiments use the natural habituation response to tell if an individual can discriminate between two categories of stimuli.…”

Individual Identity in Songbirds: Signal Representations and Metric Learning for Locating the Information in Complex Corvid Calls

“…But unlike in other songbirds, their vocalisations have not been as extensively studied, maybe because they mainly produce short, nontonal vocalisations (calls) that are often structurally complex and may involve the two-voice phenomenon. However, their vocal complexity, in combination with high levels of sociality and cognition has made corvids a suitable target for studying vocal recognition [3]. Jackdaws (C. monedula) are highly vocal, group-living corvids that breed in colonies and form strong, lifelong pair bonds.…”