Cooperative breeding influences the number and type of vocalizations in avian lineages

Abstract

Although communicative complexity is often predicted to correlate with social complexity in animal societies, few studies have employed large-scale comparative analyses to test whether socially complex species have more complex systems of communication. I tested this social complexity hypothesis in birds (Class: Aves) using the large amount of natural history information that describes both vocal repertoire and social system in these species. To do so, I marshalled data from primary and secondary records of avian vocal repertoires ( = 253), and for each of the species in the dataset I recorded the reported repertoire size and associated species information. Using phylogenetic comparative methods, I found that cooperative breeding was a strong and repeatable predictor of vocal repertoire size, while other social variables, e.g. group size and group stability, had little or no influence on repertoire size. Importantly, repertoire sizes expanded concurrently with the evolution of cooperative breeding, suggesting a direct link between these two traits. Cooperatively breeding species devoted significantly more of their repertoire to contact calls and alarm calls. Overall, these results therefore lend support to the hypothesis that social complexity via behavioural coordination leads to increases in vocal complexity.

Bioacoustic monitoring of animal vocal behavior for conservation

“…Pro-social behaviors, like cooperation, collaboration, and reciprocity (Krams, Krama, Freeberg, Kullberg, & Lucas, 2012) are posited to be facilitated by complex vocal abilities Freeberg & Krams, 2015). Termed the social complexity hypothesis for vocal communication Kershenbaum & Blumstein, 2017), it is supported both in primates and birds (Leighton, 2017;McComb & Semple, 2005). In social species, therefore, vocalizations can indicate a greater range of behavioral and demographic contexts, such as group size or composition by age and gender.…”

Structural and functional complexity of vocalizations in a cooperatively breeding passerine, Jungle Babbler

“…The major drivers of vocal complexity in avian systems include sexual selection and sociality (MacDougall-Shackleton 1997; Freeberg et al 2012) and measures of complexity include both structural (repertoire size and features of calls) and functional (behavioural contexts) aspects of vocalizations (Crane et al 2016; Holt 2017). Cooperative breeding has been found to be a strong predictor of large repertoire size in avian systems (Leighton 2017) and several avian cooperative breeders possess multiple structurally-distinct calls (Ficken et al 1978; Seddon 2002; Warrington et al 2014; Crane et al 2016). Evaluation of overall structural complexity, however, must also incorporate an assessment of the fine structure of all vocalizations by measuring the temporal and spectral features of elements (notes/syllables) that constitute a call/song.…”

“…It includes inter-group fight calls (guttural noise) produced against conspecific rivals and 6 others, including threat, distress, harsh, intermediate alert, alert, and mobbing calls that are produced against heterospecifics, mainly potential predators. This disproportionately high representation of calls towards vigilance could be because predation imposes a strong selective pressure by directly impacting the fitness of an individual (Leighton 2017). It is known that vigilance behaviour is costly since the animals must interrupt foraging in order to scan the environment for predators (Wickler 1985).…”

“…This includes Chestnut-crowned Babblers (4 out of 13 calls; Crane et al 2016), Pale-winged Trumpeter (5 out of 12 calls; Seddon et al 2002) and Black-capped Chickadees (5 out of 11 calls; Ficken et al1978). In a study carried out on 253 bird species across the globe, representing 59 families, it was found that cooperative breeders dedicated a significantly higher proportion of their vocal repertoire to vigilance related vocalizations (Leighton 2017).…”

“…Social animals exhibit higher frequency and diversity of interactions between different individuals than solitary animals and possess a larger and more complex repertoire to deliver meaningful inference (Freeberg et al 2012; Krams et al 2012; Leighton 2017). Based on the interaction type, calls are broadly classified as either ‘affiliative’ or ‘agonistic’.…”