No abstract

The ability for humans to create seemingly infinite meaning from a finite set of sounds has likely been a critical component in our success as a species, allowing the unbounded communication of information. Syntax, the combining of meaningful sounds into phrases, is one of the primary features of language that enables this extensive expressivity. The evolutionary history of syntax, however, remains largely debated, and it is only very recently that comparative data for syntax in animals have been revealed. Here, we provide further evidence for a structural basis of potential syntactic‐like call combinations in the vocal communication system of a group‐living songbird. Acoustic analyses indicate that Western Australian magpies (Gymnorhina tibicen dorsalis) structurally combine generic alarm calls with acoustically distinct alert calls to produce an alarm alert sequence. These results are distinct from previous examples of call combinations as, to our knowledge, evidence for this capacity is yet to be demonstrated in the natural communication of a non‐human species that is capable of vocal learning throughout life. These findings offer prospects for experimental investigation into the presence and function of magpie call combinations, extending our understanding of animal vocal complexity.

Comparative studies conducted over the past few decades have provided important insights into the capacity for animals to combine vocal segments at either one of two levels: within- or between-calls. There remains, however, a distinct gap in knowledge as to whether animal combinatoriality can extend beyond one level. Investigating this requires a comprehensive analysis of the combinatorial features characterizing a species' vocal system. Here, we used a nonlinear dimensionality reduction analysis and sequential transition analysis to quantitatively describe the non-song combinatorial repertoire of the Western Australian magpie ( Gymnorhina tibicen dorsalis ). We found that (i) magpies recombine four distinct acoustic segments to create a larger number of calls, and (ii) the resultant calls are further combined into larger call combinations. Our work demonstrates two levels in the combining of magpie vocal units. These results are incongruous with the notion that a capacity for multi-level combinatoriality is unique to human language, wherein the combining of meaningless sounds and meaningful words interactively occurs across different combinatorial levels. Our study thus provides novel insights into the combinatorial capacities of a non-human species, adding to the growing evidence of analogues of language-specific traits present in the animal kingdom.

The ability to recognize familiar and unfamiliar individuals is important as it plays a central role in many social interactions. Previous research has found that some animal species can discriminate among conspecifics, and recent findings indicate that some species are also able to discriminate among heterospecifics, including humans.

Many animals provide information about predator proximity in their alarm calls. In response to predators further away, Western Australian magpies (Gymnorhina tibicen dorsalis) produce alarm calls containing fewer notes compared to those produced when predators are closer. Since the ability to make fine-scale adjustments to antipredator responses by being sensitive to the level of urgency in calls may be beneficial, receivers are expected to be able to appropriately decipher and respond to this information. We conducted playbacks to test whether magpies can respond to urgency information in conspecific alarm calls. Magpies were exposed to low-urgency calls (calls with one note), high-urgency calls (calls with four notes), and one- and four-note control calls. Receivers showed greater levels of responsiveness following playbacks of high-urgency calls compared to playbacks of low-urgency and control calls, providing evidence that magpies can respond to information about the urgency of a predator threat from conspecific alarm calls.