Bird Dispersal Recordings: An Overview

Bird damage control often involves dispersing birds from areas where they cause problems. Dispersal techniques have been used at airfields, rural and urban bird roosts, livestock facilities, fruit orchards, grain fields, and other locations. Certain avian vocalizations have evolved as alarm or distress calls, and these calls can be exploited as a means of dispersing birds. The behavioral response to such calls, however, varies. Certain species may disperse with the appropriate call, whereas others show little or no reaction. The efficacy of this technique is not well documented at present, but its potential for development as a management tool seems great. Visual warning signals may increase the effectiveness of bird dispersal recordings by decreasing the habituation rate, increasing realism, or decreasing the fright threshold of the birds causing problems, or by a combination of these factors. Habitat manipulation, which reduces the attractiveness of an area to birds, complements dispersal efforts. It appears that a combination of management techniques is the most effective strategy. In addition, pretreatment evaluation of the problem and situation plus records of field results are helpful parts of a dispersal effort. Evolutionary, theoretical, and applied aspects of bird communication are discussed as they relate to bird dispersal, the repellency of recorded sounds, habituation rate, and effects of regional dialects. A review of the vocalization and hearing ranges of birds is included; this may help define the frequency and type of sounds most likely to disperse birds. The characteristics of recording and broadcasting equipment are detailed in relation to component selection, and suggestions are made for effective use. A section on field application of bird dispersal recordings provides guidelines for duration and spacing of playbacks and recommends using an integrated approach. Continued refinement of bird dispersal recordings and associated techniques can increase considerably our effectiveness in solving bird damage problems.