The effects of age on vocal mimicry in female superb lyrebirds

Avian vocal mimicry has typically been examined through the lens of sexual selection acting on males. However, the females of many bird species are accomplished vocal mimics; a fact that cannot be accounted for by traditional male-centric explanations for vocal mimicry. Female superb lyrebirds Menura novaehollandiae mimic primarily during nest defence, whilst male lyrebirds mimic predominantly during sexual advertisement. Here we examined the relationship between female age and vocal mimicry using a dataset of nesting female lyrebirds, several of which were recorded over multiple years. The vocal mimicry produced by females was diverse, and individuals varied greatly in how often they mimicked and what models they mimicked; however, neither the propensity to mimic nor the number of model sounds was explained by female age. Nevertheless, older females were more likely to mimic predators than younger females. There are two main implications of these findings. First, age is unlikely to explain intra-population variation in female mimetic repertoires. Second, females might fine-tune their mimetic repertoires as they age and mimic only models that are most effective during nest defence, such as predators. We discuss what these results mean for our understanding of vocal mimicry and vocal learning in songbirds of both sexes.