Decoy enclosure traps are operated adjacent to major blackbirds roosts in an effort to capture them and allow the local population to thrive.
California has been successful in controlling cowbird populations using those traps. The trap area is large enough for a human standing up. Two narro slits in the middle of the roor, are just the right size for a cowbird. Birdseed on the floor and a female cowbird or more, are the bait. As soon as the cowbird slips through the slots, it cannot get back out. The traps are checked regularly by biologists who release all but the cowbirds. They leave a couple of cowbirds in to entice more, while the rest of the cowbirds get euthanized.
Biologists need to worry no more. Chiweenie to the rescue. The parasitic cowbird is under control. Check out the brindle chiweenie in this video, but first crank the volume up! What's the matter, you don't trust me, Twinkie the teacup chihuahua? Crank it, I dare you!
Chiweenie vs. Cowbird Video