BLACKBIRD DAMAGE CONTROL WITH CHEMICAL FRIGHTENING AGENTS

Birds involved in damage or nuisance situations also have beneficial qualities, and most species are protected by State and Federal laws. Programs designed to alleviate bird problems, particularly those involving blackbirds, should first seek to discourage the birds from using problem areas and not to eliminate populations by direct reductional control. Habitat manipulation and mechanical frightening devices are useful techniques for discouraging bird activity, but certain chemical frightening agents have distinct advantages in some situations. We have found these agents particularly effective when used to control blackbird damage. Chemical frightening agents can be divided into two groups, the lethal and non-lethal. The latter is obviously more desirable, since accidental deaths of upland game, waterfowl, and insectivorous songbirds are minimized. Whether lethal or non-lethal, the success of these agents is largely dependent upon eliciting the desired behavioral response from unaffected birds in the population. The extreme gregariousness of blackbirds makes them ideal subjects for demonstrating the utility of this type of chemical. Personnel of the Denver Wildlife Research Center have been actively searching for and developing safe and effective chemical frightening agents since 1360. Eighty-two potential agents have been screened, but only a few have warranted field testing. Certain substituted phenyl N-methyl carbamates have shown particularly wide safety margins between temporary immobilization and death (Schafer et al., 1967)- One of these, DRC-736, has been field tested extensively and shows special promise for protecting livestock feedlots from problem blackbirds. A second compound, 4-aminopyridine (DRC-1327), described by Goodhue and Baumgartner (1965a, 1965b), has been tested at Sand Lake National Wildlife Refuge, South Dakota, since 1962 (De Grazio, 1964). This chemical frightening agent has been the most successful of the many control methods tested to alleviate blackbird damage to ripening corn