Grant: Discovery Grants Program - Individual

Many avian species are socially monogamous; a female pairs and raises a brood with a male, yet may have young that are not sired by the resident male. These extra-pair young result from fertilizations obtained by females outside the pair bond. In socially monogamous passerines, extra-pair fertilizations are typically not forced by males, but are due to females seeking them out. Obtaining good genes for the offspring is one of several possibilities why females mate outside the pair bond. The good genes hypothesis predicts that some males are of higher quality than others; females paired to high-quality males would remain genetically monogamous, while females paired to lower-quality males would obtain extra-pair fertilizations from higher quality males, resulting in large variances in male reproductive success. Females would need to assess males by one or more variable cues that are condition-dependent such that males advertise their quality honestly. Recent reviews have shown plumage colouration to be important in mate attraction and/or male-male competition. Both American robins and European starlings have extra-pair young in their broods. The objectives of the studies I am proposing are to determine in American robins and European starlings: 1) the role of plumage/bill colouration, body size, condition, and blood parasite loads in relation to mate choice, 2) whether assortative mating with respect to plumage colouration exists, 3) whether the good parent hypothesis (a positive relationship exists between ornamental expression and level of parental care) or the differential allocation hypothesis (a negative relationship exists between these two variables), holds true for nestling provisioning by adults, 4) the role of song in social and genetic mate choice by females, and 5) paternity and offspring sex ratios between first and second broods. This research is important because it is novel; none of these components have been examined together in each of these species. Publication of this research will make valuable contributions to the areas of avian mate choice, sexual selection, and parental investment. The proposed studies are also beneficial to Canadians in providing us with insights into the natural world.