Cowbirds, oh my!

One of the problems with hanging up bird feeders is that you're also attracting less desirable creatures. At the moment, that would be cowbirds. For weeks now, they have descended on our feeders, eating everything in sight. Of course, the obvious solution would be to stop feeding birds. But then I wouldn't be able to see the rose-breasted grosbeaks that are hanging around lately. They are big eaters too, but at least they don't lay their eggs in other birds' nests. We are on our last bag of birdseed now and when that's gone, they're on their own for the summer.
We are planning on adding another small native garden where birds and insects will be able to find natural food sources. And we're trying to find a bird bath with flowing water, which is more difficult than we expected.
Last Saturday, we went to Sewickley Heights park hoping to see some warblers. We saw a few towhees and I commented that we had not seen any at home lately. Shortly after we returned home we looked out the window and there was a towhee. Ask and you shall receive.