Carotenoid-based masks in the European Goldfinch Carduelis carduelis reflect different information in males and females

Abstract

Sexual selection may play an important role in the evolution of carotenoid-based signals. According to the parasite-mediated sexual selection hypothesis, organism health, parasite resistance and the expression of ornaments are linked. While some studies have analysed the expression of male carotenoid-based ornaments in relation to para- sites and immune system capacities, few studies have focused on carotenoid-derived colour patches expressed in both sexes. We analysed the relationships between endoparasite (blood and systemic parasites) loads, haematological values and the components of red mask colour in wild European Goldfinches Carduelis carduelis, a species with a carotenoid-based facial mask in both sexes. Both, males and females were assessed for immune quality and face mask expression. Face mask coloration was sexually dichromatic, males have less orange masks than females. The yellow component of the mask showed less intensity in females infected with Haemoproteus blood parasites. The total leukocyte count was inversely correlated to the yellow component of the mask in females, suggesting that mask colour reflects the immune status of females during the breeding season. Isospora infection appeared to limit the UV reflection of the red mask of females.