Floodplain ecosystems in the southeastern United States provide critical resources for resident and migratory populations of North American wood ducks (Aix sponsa). We studied radiomarked wood duck ducklings and females that nested in artificial structures and used floodplain palustrine, riverine, and lacustrine wetlands at Noxubee National Wildlife Refuge (NNWR) in Mississippi in 1996–1999 and the Tennessee-Tombigbee Rivers and Waterway (TTRW) in Alabama in 1998–1999. We estimated cause-specific mortality rates for 234 and 90 mortality events of wood duck ducklings at NNWR and TTRW, respectively. Composite estimates of duckling mortality rate for the brood rearing period across years and areas were avian (0.46; n  =  155), aquatic predators (0.23; n  =  79), snakes (0.06; n  =  21), mammals (0.05; n  =  18), exposure-related (0.02; n  =  7), and unknown causes (0.13; n  =  44). Based on this and a concurrent study, we recommend the following: 1) conserving suitable brood habitats, specifically scrub-shrub wetlands, without aggregations of nest boxes; 2) locating nest boxes amid or adjacent to these habitats in dispersed, non-aggregated arrangements; and 3) monitoring nest boxes throughout the nesting period, removing down feathers and unhatched eggs to promote use by nesting females and duckling production later in spring.