title: Egg colour reflects the amount of yolk maternal antibodies and fledging success in a songbird.
abstract: Blue-green colours in avian eggs have been proposed as post-mating signals of female phenotypic quality to their mates. Egg colour may not only indicate female value, but also the quality of the eggs themselves and of resulting offspring. To date, there has been no demonstration of an association between egg colour and egg or offspring immune quality. We here show that the intensity of blue-green colour of pied flycatcher Ficedula hypoleuca eggs reflects the amount of maternal antibodies in the yolk, a form of passive immunity crucial for offspring performance. Moreover, egg colour predicts fledging success. Also, incubating females in better condition lay more colourful eggs. The immunoglobulin level in incubating females is positively associated with that in the eggs. These results support the signalling hypothesis of eggshell coloration, underlining its role as an indicator of trans-generational transmission of immune defences in birds.
authors.affiliation: Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales-CSIC, José Gutiérrez Abascal 2, 28006 Madrid, Spain. judithm@mncn.csic.es
authors.forename: Judith
authors.initials: J
authors.lastname: Morales
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Sanz
authors.forename: Juan
authors.initials: J
authors.lastname: Moreno
mesh_terms: D000818:Animals; D004530:Egg Yolk / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D007107:Immune System; D007136:Immunoglobulins / Q000737:chemistry; D008297:Male; D008954:Models, Biological; D009425:Nesting Behavior / Q000502:physiology*; D010063:Ovum / Q000378:metabolism*; D010641:Phenotype; D010858:Pigmentation / Q000502:physiology*; D020308:Songbirds / Q000378:metabolism*; D013053:Spectrophotometry
chemical_list: C016512:IgY; D007136:Immunoglobulins