Numerous researchers have investigated survival of Mallard (Anas platyrhynchos) ducklings, but few have modeled survival of ducklings radio-marked at hatch relative to time-dependent factors. We estimated survival of 48 radio-marked ducklings for two study sites (Oakwood and Mickelson) in eastern South Dakota during summers 1998–1999. Our best-approximating model of survival indicated duckling age, study site, precipitation, and the interaction of study site and precipitation influenced survival. Survival of ducklings to 30 days was 0.42 at Oakwood (95% CI, 0.13–0.67) and 0.77 at Mickelson (95% CI, 0.42–0.92). Duckling mortality was 31.9 and 1.6 times more likely for each 1 cm of precipitation at Oakwood and Mickelson, respectively. We suggest this difference was partially attributable to greater cover of emergent vegetation at Mickelson, which potentially reduced body heat loss via evaporative cooling. Our best model also indicated daily survival increased with duckling age. Models containing daily minimum temperature received little support (w_i ≤ 0.01) indicating the covariate had negligible influence on daily survival of ducklings.