Abstract
The Class Aves is a traditional subject for studies of life-history evolution, yet the evolutionary mechanisms contributing to their diverse life-histories are still under discussion. Ricklefs (2000a) divided the history of research into life-history evolution into two periods; during the first period natural selection was established as the primary formative mechanism of life-history evolution, and during the second period (continuing until the present day) the idea that the evolutionary response to selection provided the basis for understanding variation in life-history traits among organisms was examined. In about 2000, several new perspectives were provided on life-history evolution: i.e. the evolution of life-history traits other than clutch size (e.g. developmental rate), the exploration of new selection pressures affecting life-history, and understanding the intrinsic mechanisms of the evolution of life-history. Thus more recent studies are useful in creating a foundation for the comprehensive explanation of evolutionary mechanisms of varied life-histories. In this review, I have listed and organized almost all of the environmental factors that are believed to have an evolutionary effect on avian life-history traits. Studies are separable into two types, those that detect the effects of environmental factor on individual or intra-population life-histories, and those that evaluate evolutionary change of life-history traits by means of inter-specific or inter-population comparisons. The latter approach is relatively scarce. Finally, I discuss future issues for studying avian life-history evolution and the effectiveness of studying these issues in Japan.
