Evolution of Egg Pigmentation in Passerine Birds

Avian eggs exhibit great diversity in color and markings, and are currently a source of ongoing interest in evolutionary and behavioral research. Previous research suggests that white immaculate eggs are the ancestral character, whereas background coloration and spotting evolved as the result of selection pressures by nest predators or brood parasites. The deposit of biliverdin pigment causes blue-green background color, and spotting is the result of the deposit of brown protoporphyrin pigment. Previous research on non-passerine species suggests that these two pigments evolved together. No known research has been conducted on the co-evolution of egg pigments in passerine species, which show more diversity in egg appearance than any other group of birds. I compiled data on natural history and egg shell appearance in North American passerine species to answer the questions (1) did egg pigmentations evolve together or separately among passerines? (2) Is brood parasitism pressure associated with species displaying pigmented eggs? Preliminary results suggest there is no evolutionary relationship between pigmentation types among passerine families, and parasitism pressure is unrelated to egg markings. Further analysis to control for phylogeny is being conducted