The function and evolution of ornamental traits has been a major focus of evolutionary ecology. Despite this, female ornaments have received relatively little consideration, and are still poorly understood relative to those produced by males. However, presently, there is much interest in determining how sexual selection shapes female phenotypes. Blue-green eggshell colour, derived from the antioxidant pigment biliverdin, is one attribute produced by female birds that has come under scrutiny as a potentially sexually selected trait. Based on the possibility that biliverdin is limited and costly to produce, the sexually selected egg colour hypothesis predicts that blue-green egg colour has evolved in species with biparental care as an advertisement of female quality that elicits increased paternal effort from their social mate... .
