The signaling hypothesis of eggshell coloration in birds is based on the assumption that females of species with blue-green eggs signal their phenotypic quality to their mates through deposition of the antioxidant biliverdin as pigment. Egg pigmentation may be an expression of the condition of...

Post-mating sexually selected signals are expected to indicate parental quality. The good parent model assumes that expression of the sexual character positively reflects parental ability, resulting in a potential link between the exaggeration of the character and nestling-fitness traits. We...

To understand interspecific patterns in the strength of sexual selection, variation in the costs and benefits of exercising mate choice needs to be evaluated. One manifestation of sexual selection in birds is the occurrence of greatly variable levels of extrapair paternity (EPP). A proposed...

Bird song is usually regarded as an attribute of males. However, in some species, females may also produce songs even with comparable complexity to that of males. It has been suggested that female song may evolve due to similar selection pressures acting on males, but no study has yet...

Neural correlates of bird song involve the volume of particular song nuclei in the brain that govern song development, production, and perception. Intra- and interspecific variation in the volume of these song nuclei are associated with overall brain size, suggesting that the integration of...

Bird song is usually considered to have evolved in the context of sexual selection. Because extrapair paternity is a major component of sexual selection, mating advantages at the social level for males that produce songs of high quality may be transformed into higher success in extrapair...