Female reproductive strategies and sexual conflicts in a polygynous mating system

Abstract: In this thesis, I have investigated conflicts of interest in the facultatively polygynous European starling (Sturnus vulgaris) with a focus on female reproductive strategies. The extent to which males provided parental care was a key issue in understanding the mating system of the starling. The amount of male parental care affected the quality of offspring. Polygynous males did not invest more in nestling feeding than monogamous males but provided their investment asymmetrically between their broods, predominately feeding nestlings of the primary first-mated female. Male investment in secondary females? nests was related to the length of the hatching interval. Settling patterns for secondary females varied between years and is suggested to be related to male allocation patterns and seasonal variation in the cost of delayed breeding. I found evidence of a sexual conflict over the number of breeding partners. Males gain from polygyny whereas first-mated females suffered a cost of polygyny in terms of reduced fledging success. The extent to which females were able to maintain monogamy was also examined experimentally. The possibility for females to deter or delay the settlement of other females was related to the distance between the male's two nest-sites. The pattern of female-female aggression, measured as the behaviour towards a potential female settler, was related to both the risk and cost of sharing breeding partner. The degree of aggressiveness during the pre-laying period could also be used to predict the subsequent mating status of the female. Alternative reproductive strategies of non-breeding floating females was examined and a majority of floating females used intraspecific brood parasitism to enhance their reproductive success during the period that they are excluded from breeding.