Recordings of a European starling (Sturnus vulgaris) distress call, a white noise, and a 917-Hz pure tone were presented to starlings in an outdoor enclosure to determine their relative effectiveness in frightening the birds into flight and away from a food source. Stimuli were presented during early morning hours of 2 consecutive days during summer and winter. The pure tone elicited essentially no response. Early responses (first 10 presentations) to the distress call and white noise did not differ (P > 0.05) except on the 2nd test day of winter, when the distress call received a greater early response (P 0.05). Summer responses to both sounds were greater than those in winter (P < 0.05). J. WILDL. MANAGE. 49(3):620-625 Conflicts between man and some species of birds over use of food and space have long been of concern (DeGrazio 1978). One method of controlling bird problems is to frighten the birds away from the problem site using recorded sounds. Such stimuli are non-lethal, and with the increasing concern over the humane treatment of animals (Kellert 1980, Schmidt and Bruner 1981), this aspect is quite appealing. The initial cost of the sound system for broadcasting the stimuli, the only major expenditure, can be prorated over the length of the control program (Schmidt and Johnson 1983). Auditory stimuli can be divided into two categories, biological and non-biological. The latter involves the use of devices (horns, bells, exploders, drums, etc.) to create frightening sounds. Biological sounds are those such as the communication sounds of animals. Of the biological sounds used in dispersing birds, distress calls have received the most attention (Frings and Jumber 1954, Pearson et al. 1967, Bremond et al. 1968, Schmidt and Johnson 1983). Distress calls are generally given when a bird is under physical distress as when seized by a predator, taken from a net, or handled roughly (Frings and Jumber 1954, Boudreau 1968, Perrone and Paulson 1979). There is a need to know what sound or combination of sounds should be used to most effectively frighten birds. Recorded sounds have been tested in field situations by playing a distress call or other sound to a flock of free-ranging birds and observing their reaction (Frings and Jumber 1954, Frings et al. 1955, Pearson et al. 1967, Brough 1969). Various sounds have also been compared in laboratory trials by playing a recorded sound to birds and then measuring physiological phenomena such as heart rate (Thompson et al. 1968a,b; Thompson et al. 1979) or a behavioral response (Langowski et al. 1969, Morgan and Howse 1973, Thompson et al. 1979). We evaluated the relative efficacy of three recorded sounds in frightening starlings in an outdoor cage. The sounds used, a starling distress call, white noise, and a pure tone of 917 Hz, were selected because they provided a range of biological and nonbiological sound types. White noise is analogous to white light in that the noise spectrum is uniform over a wide frequency band (Tremaine 1978). Evaluation included analysis of the early response to the sounds, later response, and habituation rate. Habituation has been defined as ... the simplest kind of learning shown by animals: learning not to respond to a repeated stimulus (Krebs 1980:103). This paper is based on thesis research by P. H. Cole (1982). We are grateful to G. D. Frederick and E. A. Pearlstein for help with recordings, E. C. Healey for producing audiospectroi Present address: Nebraska Game and Parks Commission, Lincoln, NE 68503.
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Johnson et al. (1985) studied this question.