Keep blackbirds out of the yard by installing ultrasonic technology around the perimeter to repel these pests. Ultrasonic devices drive away particular birds with sound waves imperceptible to humans. This is effective in large and small areas of property. SongbirdGarden suggests fortifying all bird feeders in the yard to ensure that blackbirds aren't allowed access.
Blackbirds take over yards and eat feeders clean in minutes, and their aggressive behavior frightens away smaller songbirds. Birds and Blooms suggests keeping blackbirds away from yard feeders by enclosing feeders in hardware cloth or chicken wire that large birds cannot fit through. An access point smaller than 2 inches restricts the access of blackbirds. Caged-in tube or tray feeders are also available at many stores and restrict access to larger birds, while allowing smaller birds to feed.
Bully birds, such as blackbirds, prefer to eat corn, millet, wheat and sunflower seeds, according to Birds and Blooms. When these foods are removed from feeders, blackbirds often go elsewhere to find sustenance. Fill feeders with seeds targeted to suit the feeding habits of more desirable birds. Safflower seeds and thistle are two types of feeds that blackbirds avoid, but are attractive to more desirable birds such as finches, nuthatches, cardinals and chickadees.