Date of this Version
Crop depredation by blackbirds (Icteridae) and Starlings (sturnus vulgaris) in North America has long prompted experimentation with control techniques. These efforts have been centered in the northeast and northcentral United States where concentrated cultivation of vulnerable crops coincides with the location where flocks of blackbirds congregate in the fall prior to their migration south (Stone, et al., 1972; Wiens and Dyer, 1975). In these areas the high cost and logistic impracticality of implementing widespread controls has suggested the need for modifying agricultural practices instead (Wiens and Dyer, 1975). More recently, attention has been focused farther south, particularly in Kentucky and Tennessee where winter roosts of mixed flocks of blackbirds and Starlings commonly number over several million birds. These highly localized concentrations have prompted concern for both agricultural damage and danger to human health (Department of Army, 1975). A major difference between the problem in the South and that farther north is that in the South the birds present themselves as much more accessible targets for control measures. By virtue of their tremendous concentrations they make the potential for large scale extermination very real. It is quite conceivable that a significant proportion of the entire North American populations of these birds could be eliminated if extermination efforts were maintained for several years at the major winter roosts. Before such extermination is allowed to proceed, a number of questions must be answered. These can be divided into two areas. The first area deals with whether or not the control measures are actually justified--how much agricultural damage is done by the birds and how real is their threat to human health? The second area of questioning concerns the environmental impact of both the control measures themselves as well as the effect of suddenly removing such large numbers of birds from the ecosystem. This paper presents the results of a preliminary study aimed not at answering these questions so much as providing some insight into the factors which must be considered if accurate answers are to be obtained.