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Some desertions by mallards (Anas platyrhynchos) could have been caused by too frequent interference on the part of the observer. Early in the nesting period, nests were visited every other day. The time between visits later was extended to a week. The only other large loss by predation was in the wheat. The author believes that losses were due in part to trails made by himself in the process of visiting the nests. The author did not believe that predators, starting at random at the edge of a large wheat field, could account for almost a third of the nests without being led to the nests by an investigator.