Abstract
We address the question of how many males a female should mate with in the context of species in which males provide care for potential offspring. Our analysis is based on the evolutionarily stable levels of parental effort of a female and a group of males. In the case of one female and two males we give a complete analysis of how the female's preference for monogamy or polyandry depends on the fitness functions assumed in the model. We then go on to consider the question of how many males a female should mate with to receive the highest level of male care. Our results are relevant in particular to the mating system of the dunnock (Prunella modularis) and also to the general question of whether a species should be monogamous as opposed to polyandrous.