My interests focus on the diversity of ecological systems, which I approach from several viewpoints. One of these is the evolutionary diversification of the life-histories of birds, emphasizing comparative and theoretical analyses of variation in life tables, including patterns of senescence, and physiological and experimental studies of growth, development, and parental care. On a higher level of ecological organization, I am investigating the historical development of ecological communities and regional species richness, using comparative analyses of diversity patterns and molecular analyses of genetic divergence. Each of these studies seeks to understand how factors that promote diversification, such as selection, speciation, and dispersal, are balanced by constraints of the system that limit response to selection or coexistence of species.