Effects of phylogeny and hatchling maturity on allometricrelationships between female body mass and the mass andcomposition of bird eggs

This review examines the allometric relationships between female bodymass and eggmass and components.The intention was to better understand howeggmass is divided between the different components in awide variety of bird species. Two hundred and fifty-two species from 21 orders are represented in the data set, which details the female body mass, initial egg mass as well as the masses of the shell, yolk and albumen for each species. Linear regression analysis techniqueswere used to determine allometric relationships between the egg components and initial egg mass or female body mass.The influence of phylogenetic relatedness was investigated using analysis of covariance and comparative analysis by independent contrasts. The effect of developmental maturity of the hatchlings was investigated using these techniques. Both phylogeny and developmental mode have significant effects on egg composition.This analysis shows thatwith regard to female bodymass, egg compositionis influenced by both phylogeny and developmental maturity and that single allometric relationships cannot be reliably applied to all bird species.Variation in egg composition in different bird species may prove to help explain other aspects of avian incubation, such as the evolution of different hatchling maturity or incubation period.