No, I leave nature alone. A lot of birds lay eggs in others nests. Just how it is.Have you learned any way to get rid of the because of their heavy parasitism? I thought I remembered that about them and when looking them up every site seems to mention the problem with them not building their own nests and laying eggs in other birds nests leaving the other bird to raise the cowbirds. http://www.audubon.org/field-guide/bird/brown-headed-cowbird
What state are you in? I pretty much get the regulars as you mentioned. I dont have the right seed mix for Cardinals. I do see them tho, just not at my feeder.We tend to get the normal birds here, Cardinals, Hummingbirds, and sparrows. There are two sparrows that sleep in the corner of our house and have been for over 6 years now, I am not sure how long they I've but they are cute and cuddle into fluffy balls in the colder seasons.
We also feed the crows, They are interesting and honestly one of my favorite. Unfortunately we had to stop feeding them this year due to a new neighbour who got Pissed and shot one that happened to be our favorite.
There is one bird feeder out back and it is birds galore there every day. It has be refilled every day. They don't seem to care who steals what. Or pig out on. I have trees way way way far back and on the sides (5 acres here), but not so much near the house, so the squirrels stealing from the birdfeeder has been a non-issue here.I notice a lot of cardinals around here. Apparently they do not mind the blackbirds stealing food. Or other birds. They just squawk about it.
Or pig out when I am not looking.