Abstract
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 females at laying or of genetic linkages between egg color and female performance variables. We have supplemented 16 pied flycatcher, Ficedula hypoleuca, females with mealworms before and during laying and compared the mass and color of their eggs as measured on the day of laying to those of 16 control females with the same nest construction and laying dates and clutch sizes. Supplemented females laid significantly heavier and more intensely blue-green eggs than control females. Egg blue-green chroma was significantly associated with the amount of biliverdin in eggshells. Egg color, and thus biliverdin content, is an expression of female condition at laying.
Highlights
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
Spectrophotometer (R400–570/R300–700) and egg BGC obtained with a MINOLTA spectrophotometer (R400–570/R360–700) (r 1⁄4 0.75, P 1⁄4 0.012)
Morales et al 2006) are mediated through general nutritional state. They show that eggshell color, and biliverdin content, reflects female condition at laying
Summary
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. According to the differential allocation hypothesis (Burley 1986; Sheldon 2000), males would contribute differentially more to parental care of offspring of females with exaggerated signals (eggs with a higher blue-green chroma), and of high quality, and females would benefit from signaling quality through improved offspring condition This application of sexual selection theory (Darwin 1871; Andersson 1994) to postmating investment is based on the crucial assumption that eggshell color is significantly associated to female condition, immunocompetence or stress (Moreno and Osorno 2003). Siefferman et al (2006) have found a positive association of egg blue-green chroma ( egg BGC) with female condition in eastern bluebirds Sialia sialis These field studies were observational and only suggest that eggshell color has informational content regarding female quality (Moreno et al 2005). We have analyzed eggshell biliverdin content and related it to egg BGC
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