Phylogenetic relatedness overshadows acoustic similarity to regulate responses toward unfamiliar mobbing calls in Masked Laughingthrushes

Recognition of heterospecific mobbing calls can occur through both innate and learned mechanisms, with the former often explained by two main hypotheses: the acoustic similarity hypothesis, which emphasizes shared acoustic features, and the phylogenetic conservatism hypothesis, which posits that closely related species may share innate decoding templates. However, it remains unclear whether phylogenetic relatedness alone can drive the recognition of unfamiliar mobbing calls, a question with important implications for understanding the evolution of interspecific communication and anti-predator strategies. We examined the recognition of unfamiliar mobbing calls in Masked Laughingthrushes (Pterorhinus perspicillatus) using playback experiments with three allopatric species' mobbing calls of Leiothrichidae family. Results revealed two key findings: (1) Masked Laughingthrushes exhibited mobbing responses to unfamiliar mobbing calls, though at significantly lower intensity compared to conspecific playbacks. (2) Phylogenetic relatedness significantly predicted mobbing intensity, independent of overall acoustic similarity. These findings improve our understanding of how birds like Masked Laughingthrush instinctively recognize mobbing calls from other species. We show phylogenetic relatedness rather than overall acoustic similarity may be a key to this innate ability. Species that share a common ancestor may possess similar built-in neural systems for decoding alarm signals. We suggest that future research needs to combine neurobiological techniques to determine how inherited biases and feature decoding system together guide variable bird communities to perceive heterospecific mobbing calls.