Fidelity of vocal mimicry: identification and accuracy of mimicry of heterospecific alarm calls by the brown thornbill

► We evaluated vocal mimicry in the brown thornbill. ► Brown thornbills predominantly imitated other species' aerial alarm calls. ► Imitations were similar but not identical to corresponding model alarms. ► Inaccurate imitations retained features important for immediate alarm response. ► We suggest alarm calls may not require perfect imitation for function.