Population Dynamics of Mallards Breeding in Agricultural Environments in Eastern Canada

Population dynamics of mallards (Anas platyrhynchos) in eastern North America likely differ relative to the midcontinent population, but independent management has been hampered by lack of data. We used data from radiomarked females from 4 sites in southern Ontario and 1 site in New Brunswick during 1992–2000 to assess demographic performance during the breeding season and to inform regional management strategies. For each site, we estimated recruitment of female young to 30 days posthatch per breeding female and projected the finite rate of population growth λ, assuming annual survival typical of the region. We constructed a matrix population model for females and conducted perturbation analyses (i.e., analytic sensitivities and elasticities) to predict response of λ to change in vital rates. Excluding 1 site, we estimated mean recruitment of 0.89 (range = 0.79–0.98). At 1 site, duckling survival approaching zero resulted in extremely low estimated recruitment (0.08). Perturbation analyses indicated that λ was highly sensitive to changes in nest survival and nonbreeding survival and moderately sensitive to changes in survival of breeding females. Recruitment for most of our sites was >2 times the mean for the Prairie Pothole Region of Canada and likely was sufficient to maintain populations despite relatively high hunting kill in the region. Despite high sensitivity of λ to nest survival, intensive management to increase nest survival likely would be inefficient because of uniform nest survival among habitats and low nest densities. Because recruitment levels were generally high but densities of breeding pairs low, we recommend protection, enhancement, and restoration of wetlands to maintain and increase habitat suitability for breeding mallards as likely the most cost-efficient management strategy to benefit populations. Relatively high hunting kill and high sensitivity of λ to nonbreeding survival imply that harvest is important to regional population dynamics and suggest the potential effectiveness of adaptive harvest management.