Threshold concentrations of an anthraquinone-based repellent for Canada geese, red-winged blackbirds, and ring-necked pheasants

Wildlife repellents provide a non-lethal alternative for managing the monetary impacts of agricultural depredation. For the purpose of developing of an effective avian repellent, we established repellency thresholds of an anthraquinone-based repellent for Canada geese (Branta canadensis), red-winged blackbirds (Agelaius phoeniceus), and ring-necked pheasants (Phasianus colchicus) in captivity. We conducted a concentration–response experiment with Canada geese offered corn seeds treated with six concentrations of Avipel® repellent (a.i. 50% 9,10-anthraquinone). Based upon our laboratory efficacy data, we used non-linear regression to predict a threshold concentration of 1450 ppm anthraquinone for geese offered treated corn seeds (i.e., 80% repellency; r2 = 0.85, P = 0.009). We also observed a positive concentration–response relationship among red-winged blackbirds offered Avipel®-treated rice (r2 = 0.70, P = 0.039) and sunflower seeds (r2 = 0.84, P = 0.010). We predicted a threshold concentration of 1475 ppm anthraquinone for blackbirds offered treated sunflower seeds. Blackbirds also reliably discriminated between untreated food and rice treated with 2325 ppm anthraquinone (F1,10 = 3414.05, P < 0.0001) or sunflower treated with 1778 ppm anthraquinone (F1,10 = 175.39, P < 0.0001). We observed a positive concentration–response relationship among ring-necked pheasants offered corn (r2 = 0.95, P = 0.001) and sunflower seeds (r2 = 0.99, P < 0.001) treated with Avipel®. We predicted a threshold concentration of 10,450 ppm anthraquinone for pheasants offered treated corn seeds. Pheasants also reliably discriminated between untreated food and corn treated with 1900 ppm anthraquinone (F1,10 = 919.86, P < 0.0001) or hulled sunflower treated with 1140 ppm anthraquinone (F1,10 = 177.35, P < 0.0001). Avipel® seed treatments effectively conditioned avoidance of treated seeds among Canada geese, red-winged blackbirds, and ring-necked pheasants. Our laboratory efficacy data provide a reliable basis for planning future field applications of anthraquinone-based bird repellents for protection of agricultural crops, property, and related natural resources. Supplemental field efficacy studies are necessary for registration of anthraquinone-based repellents for managing agricultural depredation caused by wild birds.