Bird songs are among the most beautiful, complex sounds produced in the natural world and have inspired some of our greatest poets and composers. Whilst biologists are equally impressed, their curiosity is also aroused. How and why has such an elaborate form of communication developed among birds? Charles Darwin was one of many who struggled to attempt an answer, and the elaborate songs of male birds such as nightingales clearly influenced his thinking as he developed the theory of sexual selection. Since then, biologists from many different disciplines, ranging from molecular biology to ecology, have found bird song to be a fascinating and productive area for research. The scientific study of bird song has made important contributions to such areas as neurobiology, ethology and evolutionary biology. In doing so, it has generated a large and diverse literature, which can be frustrating to those attempting to enter or survey the field. At the moment, the choice is largely between wrestling with the original literature or tackling advanced, multi-author volumes. Although our book is aimed particularly at students of biology, we hope that our colleagues in different branches of biology and psychology will find it a useful introduction. We have also tried to make it accessible to the growing numbers of ornithologists and naturalists who increasingly want to know more about the animals they watch and study.