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A variety of auditory stimuli have been used for many years as a means of repelling nuisance birds from problem areas (Boudreau, 1968; Bremond et al., 1968; Frings and Jumber, 1954; Langowski et al., 1969; Nelson and Seubert 1966; Pearson and Corner, 1967; Thompson et al., 1966, 1968a, b). This approach to alleviating bird problems is ap- pealing because wild birds are considered very sensitive to sound stimuli of biological origin, and such stimuli are harmless to both target and nontarget species. The harmless aspect is an important advantage in dealing with wildlife related problems because of the increased public concern about the safety and environmental impact of the use of chemicals to alleviate some types of problems. The major limitation to the use of auditory stimuli to effectively repel birds is that, regardless of the strength of the communication signal, there is a decrement in physiological and behavioral response with repeated stimulation, resulting in habitua- tion and loss of repellent ability. In addition, the effectiveness of sound stimuli is in- fluenced by environmental and behavioral facts such as light intensity and flock behavior (Thompson et al., 1966, 1968a). Because of these limiting factors there is a need to compare the fright producing ability of different auditory stimuli to identify the strongest stimuli for field application. To facilitate this, we developed laboratory methodology to compare repellency strength of prerecorded sound stimuli. The methodology is illustrated in the present starling study by measuring (1) heart rate (HR) as a second order function of telemetered electrocar- diogram (ECG), and (2) keypecking rate (KPR) as an operant response in a switchback experimental design for four treatments. The switchback design was used to minimize error due to between-bird-variation in slope of the habituation curve and also to reduce the number of birds required for sensitive comparisons of stimuli.