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Dryad

Pair-coordinated calling: Eurasian magpies respond differently to simulated intruder pairs that overlap or alternate their calls

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Oct 17, 2024 version files 41.58 KB

Abstract

Animal vocalisations are widely used to signal strength or motivation of a caller in competitive interactions, such as in territorial defence. Substantial understanding of signalling functions in territorial conflicts is based on singing by male songbirds. Yet, in many species, both pair members call during territorial conflicts, as well as in predator-induced situations, leading to complex signalling interactions in which calls overlap or alternate. This raises the question as to whether or not variation in how individuals in pairs time their calls is perceived as meaningful by receivers. Here, we tested with playback experiments whether Eurasian magpies (Pica pica), a species producing alarm calls (so-called chatter calls) in territorial defence, respond stronger to simulated pair-intruders who overlap their calls with each other than to those who alternate them. Magpies emitted a significantly longer first chatter in response to playback with overlapping call but tended to more closely approach the loudspeakers playing back alternating (and therefore longer) call sequences. These findings exemplify that the timing of calls by pair members matters, but in more complex ways than we predicted. The overlapping playback appeared to trigger a stronger initial chatter response but a weaker approach response, suggesting that the different ways in which magpies respond reflect different levels of arousal or defence strategies. These findings expand on classical experiments on call function, suggesting that pairs can vary the message by coordinating their alarm calls in different ways, similar to how duetting pairs time their song contributions in advertisement signalling.