Hi libirder: I'm a newbie here but have a good bit of Bluebird and Hummer experience (that's about it though!) I live in North Central GA, where Bluebirds are more common if you know what you're doing.
Just a couple of things: It may take Bluebirds 4 or 5 seasons to take to a box! They have a very large hunting/breeding area and if you have around 5 acres of OPEN, short trimmed grass, some decent sized trees and a fence line whereby they can perch and hunt, you will increase your chances of landing a breeding pair. I made the very recent mistake of putting up a feeder which attracted house finches that upset my nesting Bluebirds and Cardinals a GREAT deal. I immediately removed the feeder and things have returned to normal. In addition, you must watch out for and immediately eliminate wasp nests in unoccupied boxes - they will not nest in a box which is occupied with wasps/bees. My successful boxes have approx. 70% sun/30% shade. Bluebirds are VERY PICKY, and if their exact conditions aren't met, they will not nest in your box.
I have 20 acres with approx. 8 of them open. I have a total of 5 Bluebird boxes with normally 50% of those boxes occupied in any given breeding season. If a Bluebird can peep outside their box and see another Bluebird box, only one of those boxes will become occupied. They are not so much picky about the exact depth of a box as they are the location. No perches of course are a must, and I use very simple hollow, metal poles to mount them onto and I apply wax once a year to keep snakes, raccoons and squirrels from being able to climb up the metal pole, and feed them mealy worms in the morning as a supplement to what they hunt during the day.
Good luck and as tburke said, don't give up too early. If after 5 seasons (years), you do not have any luck, some rearranging is in order.
Just a couple of things: It may take Bluebirds 4 or 5 seasons to take to a box! They have a very large hunting/breeding area and if you have around 5 acres of OPEN, short trimmed grass, some decent sized trees and a fence line whereby they can perch and hunt, you will increase your chances of landing a breeding pair. I made the very recent mistake of putting up a feeder which attracted house finches that upset my nesting Bluebirds and Cardinals a GREAT deal. I immediately removed the feeder and things have returned to normal. In addition, you must watch out for and immediately eliminate wasp nests in unoccupied boxes - they will not nest in a box which is occupied with wasps/bees. My successful boxes have approx. 70% sun/30% shade. Bluebirds are VERY PICKY, and if their exact conditions aren't met, they will not nest in your box.
I have 20 acres with approx. 8 of them open. I have a total of 5 Bluebird boxes with normally 50% of those boxes occupied in any given breeding season. If a Bluebird can peep outside their box and see another Bluebird box, only one of those boxes will become occupied. They are not so much picky about the exact depth of a box as they are the location. No perches of course are a must, and I use very simple hollow, metal poles to mount them onto and I apply wax once a year to keep snakes, raccoons and squirrels from being able to climb up the metal pole, and feed them mealy worms in the morning as a supplement to what they hunt during the day.
Good luck and as tburke said, don't give up too early. If after 5 seasons (years), you do not have any luck, some rearranging is in order.