The sounds uttered by birds have always had a particular fascination to poets and to many ordinary people. Dr Thorpe has made a scientific study of the sounds themselves, of the circumstances in which they are uttered and of their significance; he now reviews his findings and those of his fellow scientists. To both questions: do birds sing in the musical sense and is bird-song a form of language? Dr Thorpe gives the answer yes. He then goes on to consider the functions of the various types of bird utterances. Call notes, associated with particular needs and dangers are uttered by most species as signals to their fellows, whereas continuous singing is mainly confined to male Oscines for whom it is a form of territorial and sexual display. Dr Thorpe next discusses the characteristics of the songs themselves, the way they develop in individual birds, and how they are adapted to their purposes. After considering how far songs and call-notes may be used to identify species, he concludes by describing the mechanics of sound production in birds, and the apparatus which enables such small creatures to produce such loud and complex notes.