The Pied Flycatcher is one of Europe's best-studied species. The first detailed work on it was begun in the 1930s by German ornithologists, but it was Lars von Haartman's Finnish study that both established long-term research on the species and founded many of the central themes of modern ornithology. Soon after, in the late 1940s, Bruce Campbell set up an intensive project in southwest England, which also still runs to this day. Many other eminent ornithologists followed and in 1979 Arne Lundberg and Rauno Alatalo started their own work in Sweden, Finland and latterly the north of England. A Palaearctic migrant, the Pied Flycatcher is notable for its very variable male plumage and complex territorial and polygynous breeding system. They take readily to nest boxes and have provided excellent opportunities for the study of a wide range of biological problems. This broad review of the species provides not only a detailed biology of this fascinating little bird, but a commentary on many of the most interesting problems in bird behaviour and ecology.