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Brood beat-outs were conducted in the same manner as breeding pair censuses. When disturbed, mallard (Anas platyrhynchos) and northern pintail (Anas acuta) young tended to run for upland cover. The overall effects of man's influence on duck nest success was probably somewhat greater than indicated by nest histories in this study. Not only were nests deserted early in the season because they were disturbed by nest-hunting observers, but others were destroyed by agricultural activities such as plowing, burning of stubble and pasture lands, fence building, and road construction. Man-induced disturbances were undoubtedly responsible for many unobserved losses which occurred before the crews began work in the spring or because destruction was so complete that all evidence was hidden. At worst a brood beatout is a disturbing factor, and it may take a local population several days to return to normal following it. The disturbance resulting from the observer's activities is not fully understood, but causing females and their broods to go overland would add to losses by avian predators, mammalian predators, automobiles on highways, and physical exhaustion.