| Summary: | Vocal mimicry - the copying of heterospecific sounds - is a widely spread but poorly understood phenomenon. The bowerbird family <i>(Ptilonorhnychidae) </i>are well known for their mimicry with most species incorporating mimicked calls into their elaborate sexual displays. Spotted bowerbirds <i>(Chlamydera maculata), </i>however, despite being competent imitators, do not include mimicry in their sexual displays. Here I discuss the vocal mimicry in this species, including suggestions of a possible function. I considered evidence for four hypotheses previously put forward to explain vocal mimicry. During observational studies I found that spotted bowerbirds preferentially mimic aggressive species and that the rate of mimicry also increases in the presence of such species. This suggests that mimicry may be involved in threat avoidance, as a type of Batesian mimicry. I tested this hypothesis using stuffed mounts of birds representing differing threats to the bowerbird. While there were some differences in species-specific vocalisation, such mounts did not appear to elicit a mimetic response. However, during experimental disturbances at the bower, some birds responded with an increased mimetic rate, supporting the threat avoidance hypothesis. It was evident that there was individual variation in both species-specific and mimetic vocalisation. I explored this variation in terms of duration of bower tenure and individual status. I also examined different ways to estimate the complete mimetic repertoire size. I considered different mechanisms for learning mimicry and showed that bowerbirds do not mimic the most commonly heard birds at their bowers, or the same calls as their relatives or nearest neighbours. Variation in bower design also occurs. In summary, given my data, the most likely function of vocal mimicry in the spotted bowerbird is threat avoidance.
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