Song Structure and Function of Mimicry in the Australian Magpie ( Gymnorhina tibicen ): Compared to Lyrebird ( Menura ssp. )

Abstract

This paper compares two species of songbird with the aim of elucidating the function of song and also of mimicry. It attempts to understand why some birds mimic and takes as examples the lyrebird ( Menura sp. ) and the Australian magpie ( Gymnorhina tibicen ). Mimicry by the magpie and its development has been recorded and analysed. The results show that magpies mimic in the wild and they do so mimicking species permanently settled in their own territory. So far 15 types of mimicry have been identified. One handraised Australian magpie even developed the ability to vocalise human language sounds, words and phrases. Results show that mimicry is interspersed into their own song at variable rates, not in fixed sequences as in lyrebirds. In one case it was possible to show an extremely high retention rate of learned material and a high plasticity for learning. Spectrogram comparisons of sequences of mimicry with the calls of the original species, and comparison of magpiemimicry with lyrebird mimicry is made. Both species may justifiably vie for theposition of the foremost songbirds of Australia, and both are territorial, yet the function,structure and development of song are different in the two species. It is argued thatpossible functions of mimicry are related not only to social organisation but also to theniche each species occupies. Territoriality may go some way to explaining thecomplexity of song but not necessarily the different functions of mimicry or the varyingdegrees of complexity of communication. We need to ask what conditions may fosterdevelopment of complex communication patterns in avian species.