The function of vocal mimicry in some avian displays

Abstract

Vocal mimicry in display is rare because specific identification is important. It occurs in the territorial displays of lyrebirds and bowerbirds and the reasons for this are examined. Its incorporation into the song of lyrebirds depends on the mimic using the model's calls at a time when they have no biological significance to the model and on the physical characteristics of the model's calls being significantly like those of the mimic to convey the same information to territorial rivals as do the mimic's own calls. The Noisy Scrub-bird mimics freely in sub-song but not in territorial song though it breeds in mid-winter. It has however an extended breeding season, which overlaps those of potential models and, unlike the lyrebirds, males defend their territories throughout the year. Bowerbirds mimic the calls or predators simultaneously with their own territorial song to augment its aggressive nature. Mimicry is absent from the pre-copulatory display in all these species, where highly specific visual display predominates.