Birds cause extensive damage to many agricultural crops, and most currently used methods for reducing this damage are unsatisfactory. Recent interest has focused on the use of chemical repellents which, if effective, could protect crops while having minimal adverse impacts on pest birds and other non-target animals. However, while repellents may provide relief from depredating birds in some situations, they are not the solution to all of our bird problems. The effectiveness of chemical repellents is influenced by biological factors such as the physiology of the pest animal, its hunger and motivational state, individual behavior, and social interactions. The characteristics of the food to be protected and the phenology of the crop also influence efficacy. The amount of chemical residues remaining on the crop at harvest, impacts on non-target animals, adverse effects on the growth and development of the crop and, finally, the cost of using the repellent versus the benefits to be derived all determine whether or not a repellent will be used successfully. A hypothetical idealized crop-bird complex is described for which chemical repellents should be most effective for reducing bird damage.
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