The editors of this volume approached the most distinguished authorities in avian acoustic communication and asked each to describe particularly exciting topics for current and future research. Their responses comprise a comprehensive reference on bird behaviour and animal communication. With song often serving dual strategies of territorial defence and female attraction, studies using playback techniques have shown how birds interact, how males and females differ in their perception of sound and how females might choose males on the basis of sound. Bird song has also been a model system for understanding the interaction of neural and hormonal systems in the acquisition and control of learned sounds.