You can stop starlings from nesting in martin houses by adjusting the holes instead of a circle go with 1/2 moon shape kind of squeezed down a bit. like the one in the top of the pic

The martin house I have does not have round holes. What is has was supposed to be starling-proof. They are oblong.

Well shit they work for me I guess until someone figures it out

You know, I said starlings but it's actually some bigger blackbirds. I moved my martin house and it's not out enough in the open so the martins haven't come to it like they once did so maybe that is art of the problem.

Noisy little bastards will get shot gunned for beating on my crib. Every time