Date of this Version
Blackbirds and starlings (Sturnus vulgaris) often establish large winter roosts in areas where their presence is objectionable because of economic, public health, and nuisance reasons. Several techniques are available for alleviating roost problems, including habitat manipulation, roost dispersal with mechanical and pyrotechnic devices (Mott et al 1978), and, where necessary, direct population reduction (DeGrazio 1964). These techniques, however, have limitations due to weather, roost accessibility, logistics, and adverse public reaction. In the past, 4-aminopyridine (4-AP) has been used effectively as a bird-frightening agent in agricultural crops (Besser 1976), but until now has not been adequately tested for its effectiveness as a roost dispersal agent. Two earlier small-scale tests conducted on two Colorado roosts of 10,000 and 160,000 blackbirds indicated that 4-AP-treated cracked corn baits had a potential as a roost dispersal tool (DeCino et al 1965, Schafer 1966). In January and February 1979, I conducted additional tests to assess the potential of using 4-AP for dispersing roosts, to develop techniques for bait delivery, and to determine hazards to nontarget birds.