More to explore:
Bluebirds - males prefer boxes with old nests in them - don't clean them out!
Sylvester Bird Box
Thatched Bird Box
If you discover the Bluebirds are not impressed by your efforts or your habitat, a sparrow or a wren will quickly occupy your Bluebird box if you add on a perch, or an additional entrance.
A North American Bluebird Society approved box!
Super-color bluebird houses.
Eastern Bluebird Nest Boxes