Date of this Version
There is much debate among people in bird control about whether the various methods so far developed to control bird damage are really ever cost effective (Headley, 1972; Murton and Jones, 1973; Jackson, 1976; Dyer and Ward, 1978). One thing is clear, however. The likelihood of efficacy is increased if certain conditions are met when applying a control measure. Of these conditions for control application, the most obvious one that needs to be considered, after the decision to apply some control measure is made, is "when should the application be made?" It should be clear that the control application must relate somehow to the occurrence, or expected occurrence, of bird damage in a particular field. Indeed, the usual instructions accompanying any control method include emphasis on early application presumably before birds develop a pattern of feeding in the field. But how does a farmer know when is early? Is it when he sees birds in his field? In New York, we at Cornell have observed numerous large flocks of redwings in cornfields two or three weeks before any corn damage actually occurs, so the mere presence of birds is a poor indication of damage occurrence. And, if the farmer waits until he happens to see actual damage, it may be too late for effective control. Turning to the technical literature, one can find many reports of damage occurring primarily during the milk or soft dough stage of corn development (Giltz and Stockdale, 1960; Hintz and Dyer, 1970; Stone and Mott, 1973; National Audubon Soc., undated); and many farmers are aware of this. But how can this information help a grower time his bird control application? More specific information is needed about how to recognize when corn is entering its susceptible stage and when during this stage damage is most likely to occur. In this paper, I intend to provide this type of information from my research in central New York, and propose some recommendations for its use.