Social constraints on female mate preferences in mallards, Anas platyrhynchos, decrease offspring viability and mother productivity

Constraints theory says that when individuals reproduce with nonpreferred partners, they will have offspring of lower viability than when individuals reproduce with preferred partners. To test this, we performed mate preference trials free of experimenter biases about what traits in males make them attractive to females. We eliminated social interactions that could manipulate or obscure females' choices, including interactions between males, between females, and between the sexes. We then randomly placed each female with either her nonpreferred or preferred male in breeding trials to determine how components of fitness for breeders and offspring viability varied. Offspring viability (the percentage of eggs surviving to 45 days posthatch) and mother productivity (mean number of offspring at 45 days posthatch) were significantly lower when mothers reproduced with their nonpreferred partner than with their preferred partners. This study adds to the growing list of species in which reproduction with nonpreferred partners is known to be costly to breeder and offspring fitness. It is among the few studies of birds and the only study of a species with forced copulation showing fitness deficits for offspring and mothers from enforced reproduction with nonpreferred males. 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd.