Food Supplementation and Extrapair Paternity in House Sparrows

We tested whether food availability affects extrapair paternity in House Sparrows (Passer domesticus) by providing supplemental food at their nests during some fertile periods but not others. When comparing broods produced by the same pair, a higher proportion of broods contained at least one extrapair young when food supplements were present, although the difference was not significant, and the proportion of extrapair young per brood was higher when food supplements were present, although again the difference was not significant. There was also little evidence that the presence of food supplements affected the amount of time spent at the nest by males, females, or both sexes at the same time. We also conducted two smaller experiments designed to either increase or decrease the rate at which individuals encountered one another but found no concomitant increase or decrease in the rate of extrapair paternity. Overall, we found little evidence food distribution affects extrapair paternity in House Sparrows.