Guys, I solved my own brown-headed cowbird and grackle invasion by repalcing my feeders with the saucer type receptacle to limited access feeders with ports where birds have to reach in and get one seed at a time rather than raking the seed out of the saucer part with their beaks to the ground for the flock. Seed disappears quickly like this. Purple grackles and cowbirds can't take the frustration of "one seed at a time" and dissapear. Mine did in less than a few days, and I live in an open, rural area where thousands are sighted, but I feed none of them, and use much less black-oil seed. These things are design genius!
Blessed, and in His grip, Dan Brown (not the author dude!)