With more than 10,000 species that vary in size, use diverse habitats that extend across latitudes and altitudes, consume a wide variety of food items, differ in how they fly (or not), communicate, and reproduce, and have different life histories, birds exhibit remarkable variation in form (anatomy) and function (physiology). Our understanding of how natural selection has generated this variation as birds evolved and as different species adapted to their unique circumstances has grown considerably in recent years. In In a Class of Their Own: A Detailed Examination of Avian Forms and Functions, this variation is explained in great detail, beginning with an overview of avian evolution and continuing with information about the structure and function of the avian skeleton, muscles, and the various body systems. Other chapters focus on avian locomotion (including flight), migration, navigation, communication, energy balance and thermoregulation, and various aspects of avian reproduction, such as nests and nest building, clutch sizes, and parental care. In a Class of Their Own: A Detailed Examination of Avian Forms and Functions will be must reading for anyone, professional or non-professional, who needs or wants to learn more about birds.