Behavioral Ecology and Sociobiology

, Volume 61, Issue 6, pp 863–876 | Cite as

Are blue eggs a sexually selected signal of female collared flycatchers? A cross-fostering experiment

  • Miloš KristEmail author
  • Tomáš Grim
Original Paper


Impressive variation in egg colouration among birds has puzzled evolutionary biologists for a long time. The most frequently studied selective forces moulding egg colouration—predation and brood parasitism—have either received little empirical support or may play a role in only a minority of species. A novel hypothesis has suggested that egg colour may be significantly influenced by sexual selection. Females may deposit a blue-green pigment biliverdin into eggshells instead of using it for themselves as a powerful antioxidant. By this handicap, females may signal their quality to males, which are then hypothesized to increase their paternal effort. We experimentally tested the hypothesis in the collared flycatcher (Ficedula albicollis), a species laying blue-green eggs. We cross-fostered clutches between nests to disentangle effects of female/territory quality and egg colour on paternal effort and nestling quality. The results supported two assumptions of sexual signalling through egg colour hypothesis: Blue pigment seems to be a limited resource for females, and female quality is positively correlated with the intensity of the blue-green colour. However, we did not find support for the main prediction of the hypothesis, as male parental effort parameters (feeding frequencies to nestlings and intensity of nest defence) were unrelated to egg colour. We discuss possible reasons for the discrepancy between our results and previous correlative analyses that supported the hypothesis that blue egg colour may be a postmating, sexually selected signal in females.


Egg colour Differential allocation Female signalling Immunity Parental investment 



We thank Vladimír Remeš, Manuel Soler, Karel Weidinger, and several anonymous referees for valuable comments and/or discussion on the manuscript. We owe J. Stříteský and forest enterprise Prostějov for providing the nest-boxes. T. Koutný helped with the analyses of video records. We are grateful to Dana Cambell for correcting our English. M. K. thanks Kačka for support. This study was supported by grants from the Czech Ministry of Education (MSM 6198959212) and from Grant Agency of the Czech Republic (No. 206/03/D234 and 206/03/0215). The experiments were done under the license from The Central Commission for Animal Welfare of the Czech Republic (No. 065/2002-V2) and in accordance with the laws and ethical guidelines of the Czech Republic.


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Museum of Natural HistoryOlomoucCzech Republic
  2. 2.Department of ZoologyPalacký UniversityOlomoucCzech Republic

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