Mallard and Black Duck Breeding Parameters in New Brunswick: A Test of the Reproductive Rate Hypothesis

Abstract

Divergent population trends of mallards (Anas platyrhynchos) and black ducks (Anas rubripes) in eastern North America have been attributed to differences in reproductive rates. In order to test this hypothesis, we compared breeding parameters of radiomarked mallards and black ducks in an agricultural environment in midwestern New Brunswick. No differences in clutch size, nest success, hen success, duckling survival, or hen survival were detected during the breeding season. Reproductive success of both species appeared to be at or above the level needed to maintain population size. These results support a growing body of evidence that mallards are not more productive than black ducks in agricultural or forested environments. Moreover, earlier studies indicate no difference in annual survival rates between the 2 species. Given the failure of this and other studies to detect differences in vital rates of the 2 species, divergent population trends of mallards and black ducks present somewhat of a paradox. We hypothesize that differences in the population status of mallards and black ducks are the result of differences in breeding propensity that may arise from competition for breeding resources.