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Aim Geographical disparities in the effect of the environment on population dynamics have been shown to follow a core-periphery gradient when peripheral populations are less abundant and occur in marginal habitat. Whether the gradient in environmental influence occurs in the absence of a gradient in abundance is not known. We tested whether duck populations on the periphery of their main breeding region were more strongly affected by environmental stochasticity and less abundant than at the core. Location The Prairie Pothole Region of central United States and Canada Methods We used the North American Waterfowl Breeding Population and Habitat Survey to model the dynamics of 10 duck species at 1059 sites spanning 1961-2012. We used the North American Breeding Bird Survey to measure abundance at the same sites, averaged over the same time span. We used structural equation models to characterize relationships among a site's distance from the regional centre, a site's abundance, and the degree to which a site's ducks were affected by environmental stochasticity. Results Environmental stochasticity never strongly contributed to population dynamics in the region's core. However, we did not find a linear increase in environmental stochasticity with increasing distance from the core. For seven species, we found that environmental stochasticty was stronger in sites of lower abundance. For only two species did average abundance decline from the region's core to periphery. Main conclusions Variability in the magnitude of environmental stochasticity follows coarse spatial differences in wetland productivity. Yet, among peripheral sites, the contribution of the environment to population dynamics varies, possibly reflecting the importance of the local environment and dispersal. [ABSTRACT FROM AUTHOR]

Early hatched waterfowl are more likely to enter the breeding population. Managers' primary tool to increase nesting success in the Prairie Pothole Region (PPR) of North America is managing upland vegetation for duck nesting cover. To determine whether managed covertypes affect early-season nesting success, we modeled seasonal variation in nesting success using >17,000 duck nests found in managed and unmanaged covertypes in prairie Canada from 1993 to 2000. Nesting success was higher in most managed covertypes than in unmanaged covertypes early in the nesting season. Planted cover appeared to be the best managed covertype for increasing early-season nesting success as it had high early-season nesting success, and was selected by nesting ducks in greater proportion than its availability; however, nesting success in planted cover declined later in the nesting season while nesting success in most unmanaged covertypes increased. Nevertheless, even with reduced nesting success late in the season, planted cover was more productive than surrounding unmanaged covertypes. Future waterfowl management efforts should focus on providing safe nesting cover early in the nesting season. [ABSTRACT FROM AUTHOR]

Examines variation in female mallard survival rates from nonhunting sources across Canadian Prairie Pothole Region. Influence of age on survival probability; Relationship between female survival and periods of nesting season; Importance of female survival in mallard population.