Evolution of life-history variation among species of altricial birds

A unified approach is developed for the comparative structure of bird life histories. It combines four basic components (individual production rate as a function of adult body size, stable demography, inter-generational competition for breeding sites, and natural selection for an optimal size) to predict both the powers and intercepts of the interspecific allometries of life-history variables to adult size. The theory also predicts when a taxon should deviate from the interspecific scaling lines. Finally, the theory predicts (or makes use of) several dimensionless numbers, particularly the ratio of non-breeders to breeders.