The Flexible Phenotype attempts a true synthesis of physiology, behaviour, and ecology by developing an empirical argument that describes the intimate connections between phenotypes and their environments. It portrays an ecological angle to the rapidly growing extended synthesis in evolutionary biology that incorporates developmental processes, self-organization, and the multiple dimensions of inheritance. The book starts with a synthesis of the principles guiding current research in ecophysiology, functional morphology, and behavioural ecology. Each aspect is illustrated with the detailed results of empirical work on as wide a range of organisms as possible. The integrated story of the flexible phenotype is woven throughout the book on the basis of the authors' long-term research on migrant shorebirds and their invertebrate prey. These birds travel vast distances from one environment to another, and the changing nature of their bodies reflects the varied selection pressures experienced in the course of their globe-spanning migrations. In essence, the authors argue for the existence of direct, measurable, links between phenotype and ecology, mediated by developmental processes. Their book outlines a more encompassing approach to evolutionary ecology, based on first principles in physiology, behaviour, and ecology. It aspires to encourage a further integration of ecology and physiology, as well as fostering a collaborative research agenda between ecologists, physiologists, and developmental biologists.