U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version

October 2004


Published by Proc. 16th International Sunflower Conference, Fargo, ND


One issue affecting sunflower growers in the upper Great Plains of North America is crop depredation by blackbirds. In this region, blackbirds annually destroy an average of $5.4 million of sunflower. To increase the understanding of how blackbirds are influenced by large-scale land-use patterns, we developed multiple regression models to explain how various land use patterns influence blackbird abundance. We used data from the North American Breeding Bird Survey and the USGS land cover assessment to develop regression models examining associations between land use characteristics and blackbird abundance. Both red-winged blackbirds and yellow-headed blackbirds were negatively associated with the amount of developed area, while the amount of wetland area strongly influenced yellow-headed blackbird abundance. Common grackles were positively associated with the number of land-use types in the landscape. These associations can be partially explained by habitat preferences of these species; however, many variables that would seemingly be good predictors of blackbird abundance were not significant. This result suggests that either a greater number of samples are needed to identify these associations, or the relationships in question are not detectable at the landscape level.