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I'm sure all of you have often heard of bird control methods which were successful in one place and failures elsewhere. Perhaps you have experienced these results yourself. Quite often, bird control apparatus or concepts are condemned as failures when actually other factors are responsible. Today, I shall explain some of the reasons these discrepancies occur. My observations, over a period of 15 years, reveal that birds' responses to alarm stimuli varies with environmental conditions, clocktime, physiological requirements, social structure, species, and other factors. All of the observations reported herein were made under natural conditions while researching methods to reduce bird depredations in agri-cultural crops, and to eliminate bird collisions with aircraft in or near airports and air bases. These problems have not been widely publicized but nevertheless are very real and, at times, quite serious. Birds receive most of their information through the eyes and the ears, and these sensory mechanisms have been well studied. The avian tactile (touch) sense has received little attention and this may prove to be another important channel of information. The other two senses, smell and taste, are regarded by most authorities as being less well developed. Taste, however, is important to birds in that it allows them to discriminate between preferred foods and, in some species, to detect minute traces of foreign material, such as toxicants. In this paper, however, only visual and acoustic alarm stimuli are discussed.