Date of this Version
During late summer and fall, a hectare of cattail in a cattail-dominated wetland can hold about 1500 blackbirds. Thus, even small wetlands of 5-1 0 hectares that become roosts can cause significant problems for sunflower producers. USDA Wildlife Services has a cattail management program in North Dakota and South Dakota that helps sunflower producers eliminate cattail vegetation near susceptible fields. However, cattail-reduction treatments (which typically occur in August or September) do not break the cattail stalks, and the roosting substrate remains in place until the following year. Moreover, the sites selected for treatment are generally signed up at least one-year ahead, which presents problems for sunflower producers that have blackbird roosts developing rapidly in unexpected locations near their ripening fields.
Given the vast number of wetland roosting sites available in areas of major sunflower production, a roost dispersal method is needed that brings immediate effect, has low costs, and is safe and easy to deploy. Laser beams have been used effectively to disperse night roosts of double-crested cormorants. We tested the field effectiveness of moderately-powered lasers for harassing blackbirds attempting to roost in cattail.