Pairs of adult black ducks (Anas rubripes) were fed a diet containing 0, 4 or 40 ppm cadmium as cadmium chloride. One-week-old ducklings that had been fed the same dietary concentrations of cadmium as had their parents were tested for avoidance of a fright stimulus. Ducklings fed 4 ppm cadmium ran significantly farther from the stimulus than did controls or ducklings fed 40 ppm cadmium. Such an alteration in behavior could have harmful effects on wild birds.