This is the first re-appraisal in 50 years of concepts of development made in birds. This book is a case study in evolutionary diversification of life histories. Although birds have a rather uniform body plan and physiology, they exhibit marked variation in development type, parental care,and rate of growth. Altricial birds are fully dependent on their parents for warmth and nutrition and begin posthatching life in a more or less embryonic condition. At the other extreme, such superprecocial species as the megapodes are independent of all parental care from hatching, and theneonate, able to fly, resembles an adult bird. This book thus attempts to present an integrative perspective of organism biology, ecology, and evolution.