Date of this Version
2017. Pp. 84-88.
Animals attempt to maximize foraging efforts by making strategic foraging decisions. Foraging efforts can be influenced by chemically defended food. Food resources that are chemically defended force foragers to balance the nutritional gain with the toxic costs of foraging on a defended food resource. Chemical defense, in this case sunflower treated with chemical repellent, may be capable of deterring birds from foraging on treated crops. Blackbirds (Icteridae) cause significant damage to sunflower (Helianthus annuus) with damage estimates of $3.5 million annually in the Prairie Pothole Region of North Dakota, the largest sunflower producing state. Chemical repellents may be a cost-effective method for reducing bird damage if application strategies can be optimized for sunflowers. Anthraquinone-based repellents have been shown to reduce feeding on sunflower achenes by more than 80% in lab studies, but results in the field are inconclusive due to application issues where floral components of sunflower result in low repellent contact with achenes. Ground rigs equipped with drop-nozzles have shown promise in depositing repellent directly on the sunflower face but coverage is variable. We propose to evaluate the feeding behavior of red-winged blackbirds (Agelaius phoeniceus) and the efficacy of an anthraquinone-based avian repellent when applied directly to the sunflower face in a lab-based experiment. Our main objectives are to 1) evaluate the coverage needed on the face of the sunflower to establish repellency, 2) evaluate achene removal rates over time to understand time to aversion at varying repellent coverages, and 3) evaluate the feeding behavior and activity budgets of red-winged blackbirds on treated and untreated sunflower. The results of this study will inform repellent coverage needed at the scale of the sunflower plant to deter feeding or alter time budgets of foraging red-winged blackbirds to ultimately reduce sunflower damage.