This book augments discussions of behavioural ecology with a comprehensive study of a single species, using it to illustrate and discuss many theoretical issues. Taking the shelduck as its principal example, the book considers how an animal's behaviour helps it to survive and reproduce in a hostile environment. It also discusses the effects of behaviour, particularly social behaviour, in the limitation of animal population size. The arrangement of the text follows the phases of the shelduck's annual cycle and discusses the different behavioural problems encountered at each stage. In this account a wide variety of topics in behavioural ecology have been brought together and applied to a thorough field study of this highly territorial species.