Starlings are usually the species involved.
Livestock operations within 20 miles of winter roosts are susceptible to invasion by blackbird flocks, especially when snow covers the ground. The open food supplies and protection afforded by open livestock housing provide desirable habitat for these flocks. Blackbird depredations at feeding operations most often are associated with open feed troughs. For small operations, the problem often can be eliminated or significantly reduced by converting to enclosed feeders. Trapping and shooting.