title: Eggshell colour does not predict measures of maternal investment in eggs of Turdus thrushes.
abstract: The striking diversity of avian eggshell colour has long fascinated biologists. Recently, it has been proposed that the blue-green colour of some eggs may function as a post-mating sexually selected signal of female phenotypic quality to their mates to induce higher allocation of paternal care. It has been suggested that maternally deposited yolk carotenoids may be the specific aspect of reproductive quality that the female is signalling via eggshell colour. We use the known properties of the thrush visual system (Turdus sp.) to calculate photon capture for the four single cone photoreceptors, and the principal member of the double cone class for eggs in clutches of two introduced European thrush species (Turdus merula and Turdus philomelos) in New Zealand. We show that differences in the avian-perceived colours of individual eggs are not consistently correlated with different measures of maternal investment in the egg. Given the growing extent of the knowledge between maternal quality, parental investment and eggshell pigmentation across avian taxa, we encourage the use of avian perceptual modelling for testing alternative non-signalling explanations for the structural and physiological basis of these relationships.
authors.affiliation: Centre for Ornithology, School of Biosciences, Birmingham University, Birmingham, UK. p.cassey@bham.ac.uk
authors.forename: Phillip
authors.initials: P
authors.lastname: Cassey
authors.forename: John G
authors.initials: JG
authors.lastname: Ewen
authors.forename: Tim M
authors.initials: TM
authors.lastname: Blackburn
authors.forename: Mark E
authors.initials: ME
authors.lastname: Hauber
authors.forename: Misha
authors.initials: M
authors.lastname: Vorobyev
authors.forename: N Justin
authors.initials: NJ
authors.lastname: Marshall
mesh_terms: D000818:Animals; D003116:Color; D003118:Color Perception; D017753:Ecosystem; D004528:Egg Shell / Q000737:chemistry*; D005260:Female; D008425:Maternal Behavior; D009520:New Zealand; D017785:Photons; D010786:Photoreceptor Cells / Q000502:physiology; D020308:Songbirds / Q000502:physiology*; D013045:Species Specificity; D014796:Visual Perception