Behavioral Ecology and Sociobiology

, Volume 62, Issue 12, pp 1877–1884 | Cite as

Egg pigmentation reflects female and egg quality in the spotless starling Sturnus unicolor

Original Paper


It has been proposed that blue colouration in eggs has evolved as a signal of female quality that males can use to modulate their parental investment. This hypothesis is based in the antioxidant properties of biliverdin whose costly deposition in the eggshell is expected to signal female antioxidant capacity and egg quality. Since maternally derived androgens are costly to produce and may adaptively affect offspring phenotype, high-quality females may benefit by signalling their androgen investment through egg colouration. Our aim was to investigate whether egg colour variation in the spotless starling reflected the amount of pigments on the eggshell and whether egg pigmentation was related to female and egg quality. Chromatography analyses revealed that spotless starling eggshells contained two different pigments: biliverdin and protoporphyrin IX with no correlation between them. Biliverdin contents correlated positively with egg colouration indicating that darker eggs with a higher peak in the blue–green segment of the spectrum contained higher amounts of biliverdin. Eggs containing more biliverdin were laid by high-quality females and contained higher yolk testosterone levels. However, despite the strong correlation between biliverdin and colorimetric variables, egg colouration did not reflect accurately female and egg quality. Our results provide evidence that eggshell pigmentation in the spotless starling is related to female and egg quality as shown by the yolk testosterone levels. However, the lack of relation between egg colour and female condition and egg quality do not provide evidence to support the signalling function of egg colouration.


Egg pigments Biliverdin Yolk androgens Spotless starling 



We are grateful to Montserrat Gil for helping at the field and to Ana Martinez for assistance with colorimetric measurements. IL was supported by Ph.D. grants from CONACYT (México). Research was funded by a grant (BOS2002-00105) and a Ramon y Cajal fellowship from the Ministerio de Educación y Ciencia (Spain) to DG. Permission to work in the study area was granted by the Ayuntamiento de Soto del Real and the Consejería de Medio Ambiente of the Comunidad Autónoma de Madrid. This manuscript is a contribution of the field station “El Ventorrillo”. The experimental procedures for this study comply with the current laws for the treatment of animals in behavioural research and were approved by the Spanish Ministry of Education and Science (BOS2002-00105).


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.Departamento de Ecología EvolutivaMuseo Nacional de Ciencias Naturales (CSIC)MadridSpain
  2. 2.Institute of PhysiologyAcademy of Sciences of the Czech RepublicPragueCzech Republic

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