Yolk and Feather Carotenoids in Relation to Female Condition and Reproduction in the Yellow-headed Blackbird (Xanthocephalus Xanthocephalus)

Abstract

ABSTRACT. Carotenoids can be important antioxidants and immunostimulants for developing embryos and adult birds, and they are often incorporated into colorful sexual displays as signals of individual quality. The allocation of carotenoids to egg yolks and feathers can be affected by a female's physical condition, which can in turn affect offspring growth and survival. We examined relationships between yolk and feather concentrations of carotenoids and various indices of female quality (i.e., body condition, heterophil-to-lymphocyte ratio, hematocrit, date of nest initiation, egg mass, reproductive success) in the Yellow-headed Blackbird (Xanthocephalus xanthocephalus), a brightly colored passerine. Measures of physical condition of female Yellow-headed Blackbirds were correlated with the allocation of carotenoids to both eggs and feathers. Specifically, less stressed (i.e., lower heterophil-to-lymphocyte ratio) females had higher concentrations of β-carotene in their eggs than females that were more stres...