A number of biparental avian species once thought to be monogamous are now recognized to be socially monogamous and seek copulations with individuals outside of their social pair. Having a greater number of partners may benefit females by increasing the genetic diversity of their offspring. Females would be aware of the number of partners they had during the egg laying phase of a breeding attempt and we hypothesize that they would invest more in a clutch that had a higher probability of extra-pair young (EPY). We predict that maternal care, measured as nest visitation rates using radio frequency identification, would be higher in nests with the presence of EPY. We monitored maternal and paternal care, and extra-pair paternity rates of 27 song sparrow (Melospiza melodia) nests (37 individuals) in 2018 and 2019. Maternal visitation rates were higher in nests with EPY compared to clutches without EPY (p value = 0.0294). Additionally, maternal visitation rates increased with the number of extra pair offspring present in the nest (p value = 0.0273). Paternal visitation did not differ across EPY and non-EPY nests. This supports the idea that females invest more in nests with higher rates of extra-pair paternity. However, visitation rates are only a proxy of maternal investment. Despite higher maternal visitation, nests with EPY were less likely to fledge. Future studies should look at rates of extra-pair copulations and female investment to further examine female mate choice and maternal investment.