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 magpie

mimicry with lyrebird mimicry is made. Both species may justifiably vie for the

position 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 that

possible functions of mimicry are related not only to social organisation but also to the

niche each species occupies. Territoriality may go some way to explaining the

complexity of song but not necessarily the different functions of mimicry or the varying

degrees of complexity of communication. We need to ask what conditions may foster

development of complex communication patterns in avian species.