Optimizing the use of decoy plots for blackbird control in commercial sunflower

In 2004, USDA's Wildlife Services began to cost share 8-ha Wildlife Conservation Sunflower Plots (WCSP) with sunflower growers to lure migrating blackbirds away from commercial sunflower fields. During late summer and fall of 2004 and 2005, blackbirds used sunflower more than other crops, especially WCSP placed near blackbird roosts. Blackbird density in WCSP and commercial sunflower was negatively associated with nearby habitat types (<2.4 km) that provided alternative foraging locations, including hectares of sunflower, wheat, and fallow lands. Blackbird density was positively associated with shelterbelts, wetlands, and unused habitats, such as soybean fields. Blackbird damage was lower in commercial sunflower fields closely associated with WCSP (≤2.4 km) than commercial sunflower fields >10 km from WCSP. Across both years, birds removed an average of 435 kg/ha and 49 kg/ha of sunflower seed in WCSP and commercial sunflower fields, respectively. Additionally, in 2005, blackbirds removed 181 kg/ha of seed in commercial sunflower >10 km from WCSP (reference fields). WCSP had a cost-benefit ratio of 3.4:1; however, in reference sunflower fields, birds removed 3.2 times more sunflower seed than in commercial sunflower fields near WCSP. Our data suggest that producers should consider planting cost-shared WCSP as part of an integrated pest management strategy to reduce blackbird damage to commercial sunflower.