I examined timing of reproduction and productivity in box-nesting House Wrens (Troglodytes aedon) inhabiting three riverbank woodlands subjected to different levels of flooding. In years when the North Platte River flooded its banks submerging ground foraging substrates, dates of nest initiation and egg laying in two wren populations were delayed and nonsynchronized. In contrast, timing of breeding was unrelated to annual variations in water levels or spring weather in wrens occupying a riparian area buffered from flooding. Rates of nest predation were unlikely to influence timing of laying because they did not vary among years or between early and late nests in any locality. Initial clutch size declined seasonally in all populations and was smaller in years when breeding was delayed by flooding. At all localities, variation in numbers fledged from successful nests was related to interactions between year and laying date. Generally, more nestlings fledged from early nests because clutches were larger. In addition, early clutches lost fewer young than late clutches of equal size in the population most impacted by flooding. Greater fledging success may select for early laying and may explain higher laying synchrony in early years.