This female has staked out one of the nesting boxes on my property. We've been raising bluebirds for over 12 years and generally will see 5 or more succesful hatchings. I'd guess that at least 75% of them resulted in 6 young. If you think you have sufficient space I'd recommend putting up a box and wait and see. I get mine at Lowe's where they cost around $10.oo for the ones made from cedar. I keep saying I'm going to build some but for that price it's hardly worthwhile. I put the box at about 7 or 8 feet off the ground and leave about 30 feet of open flight space at the front. I use aluminum conduit with rebar inside for additional stability and spread a bit of vaseline on the conduit to prevent ants from climbing. I have a few snakes on the property but I've never lost a nest to them that I know of so I don't bother with guards.