This book provides everything from basic knowledge to the recent understandings of avian reproductive physiology, covering many unique aspects. It will inspire avian biologists as well as researchers in varied fields and will offer important steps towards better fertilization success in birds. In spite of the recent remarkable developments in modern technology, a comprehensive understanding of the reproductive mechanisms is still far in the future due to the diverse reproductive tactics in vertebrates. Birds have highly refined reproductive strategies and some of those strategies are unique to birds. However, together with ongoing progress of the genome analysis of birds and the crying need for further increase in meat and egg production, research on avian reproduction is now accelerating and becoming more important. With contributions by leading scientists, the book explains avian primordial germ cells; the sex-determining mechanism; reproductive endocrinology and immunology; sperm, egg, and egg coat; sperm–egg interaction; polyspermic fertilization; seasonal reproduction; social triggers; hormonal and behavioral changes; broodiness; oviductal sperm storage; and biotechnology. This book is recommended for all researchers and students who are interested in birds or reproduction.