Nest and brood survival of Ring-necked Ducks in relation to anthropogenic development and wetland attributes

摘要

The boreal and hemiboreal forests are facing increasing anthropogenic development in areas that have traditionally been remote and inaccessible. Although these forests are recognized as important to breeding waterfowl, breeding season vital rates and the influence of anthropogenic development on these rates remain largely unexplored. I estimated nest and brood survival of Ring-necked Ducks (Aythya collaris) in the hemiboreal forest of Minnesota. I located 115 nests on 43 wetlands, radio-tagged 65 nesting hens, and monitored 32 broods. I considered the influence of distance to and density of buildings and roads, and road-surface type, as well as wetland characteristics and other variables hypothesized to influence waterfowl vital rates. The best-supported nest survival models included covariates for distance from the nest to nearest road and road-surface type. Nest survival declined with increasing distance from roads and was higher for nests near paved roads, at least when the distance was < 400 m. However, an interaction term in the top-ranked model suggested the effect of road type varied as a function of distance from nest. The model-averaged estimate of 35-day nest survival, based on the top two models was 0.278 (SE = 0.048). Brood survival increased with brood age and open water area, and decreased with nesting habitat area and distance from open water to nearest road. Cumulative brood survival to 30 days was 0.263 (SE = 0.035). These findings indicate that roads may influence both nest and brood survival. Furthermore, higher brood survival at wetlands with less nesting habitat area and more open water area may explain why hens move broods. Conservation managers should consider how habitat needs change throughout the breeding season to adequately address the needs of Ring-necked Ducks. Further study is needed to understand how anthropogenic development can be incorporated into conservation planning.