Higher-order sequences of vocal mimicry performed by male Albert's lyrebirds are socially transmitted and enhance acoustic contrast

Abstract

Most studies of acoustic communication focus on short units of vocalization such as songs, yet these units are often hierarchically organized into higher-order sequences and, outside human language, little is known about the drivers of sequence structure. Here, we investigate the organization, transmission and function of vocal sequences sung by male Albert's lyrebirds ( Menura alberti ), a species renowned for vocal imitations of other species. We quantified the organization of mimetic units into sequences, and examined the extent to which these sequences are repeated within and between individuals and shared among populations. We found that individual males organized their mimetic units into stereotyped sequences. Sequence structures were shared within and to a lesser extent among populations, implying that sequences were socially transmitted. Across the entire species range, mimetic units were sung with immediate variety and a high acoustic contrast between consecutive units, suggesting that sequence structure is a means to enhance receiver perceptions of repertoire complexity. Our results provide evidence that higher-order sequences of vocalizations can be socially transmitted, and that the order of vocal units can be functionally significant. We conclude that, to fully understand vocal behaviours, we must study both the individual vocal units and their higher-order temporal organization.

Selective alarm call mimicry in the sexual display of the male superb lyrebird (Menura novaehollandiae)

“…In birds that acquire their vocal mimicry via vocal production learning (sensu Vernes et al 2021), an individual can develop vocal mimicry either by copying the model species directly or by copying the mimicry produced by conspecifics (Dalziell et al 2015). There is good evidence that male Albert's lyrebirds M. alberti learn their vocal mimicry from both the models directly and from other male lyrebirds (Putland et al 2006;Backhouse et al 2022) and both mechanisms may be at play in male superb lyrebirds too (e.g., Smith 1988). It seems unlikely social transmission alone would be sufficient to maintain the complex acoustic illusion of a mixed-species mobbing flock males produce, of which mobbing alarm calls is only one component .…”

Higher-order dialectic variation and syntactic convergence in the complex warble song of budgerigars

“…When colonies come into contact, these differences are lost rapidly. A few months after contact, the syntactic structure of warble sequences had converged, and males from both erstwhile colonies sang warbles with similar syntactic structures, Syntax in animal sensory signals is both diverse and complex, with considerable variety in its form and function (Arnold and Zuberbühler, 2006;Backhouse et al, 2022;Bhat et al, 2022;Briefer et al, 2013;Engesser et al, 2016;Isaac and Marler, 1963;Kershenbaum and Garland, 2015;Kershenbaum et al, 2012;Kershenbaum et al, 2016;Leroux et al, 2021;Ligon et al, 2018;Scholes III, 2008). The structure of vocal sequences, particularly in vertebrates is known to convey information about context and behavioral state (Bhat et al, 2022;Ciaburri and Williams, 2019;Engesser et al, 2016;Leroux et al, 2021;Suzuki et al, 2018).…”

“…For example, members of a species may change the structure of a single element in a signal, or the temporal structure (syntax) of an acoustic signal sequence to convey information (Bhat et al, 2022; Bohn et al, 2009; Engesser et al, 2019; Leroux et al, 2021; Suzuki et al, 2018; Zuberbühler, 2018). The larger the repertoire of elements, the greater the combinatorial diversity of sequences, and the more complex the information content of signals (Backhouse et al, 2022; Balsby et al, 2017; Clay and Zuberbühler, 2011; Dalziell and Welbergen, 2016; Leroux et al, 2021; Mitoyen et al, 2019; Scholes III, 2008). In addition to behavioral state, group-living animals may use complex signals to communicate group or individual identity (Mammen and Nowicki, 1981; McComb et al, 2000; McCowan and Hooper, 2002).…”

Depleted cultural richness of an avian vocal mimic in fragmented habitat

“…Previous research suggests that male lyrebirds learn their mimicry from both other lyrebirds and heterospecifics (Backhouse et al, 2022;Putland et al, 2006), and so male mimetic repertoires are expected to be sensitive to processes affecting both lyrebird populations and the diversity and abundance of model species.…”