Using the simple plan you can build a Bluebird house instantly. Free directions this way!
Many bird enthusiasts put up bluebird houses specifically designed just for the bluebird.
The correct size of hole helps deter predators while making it easier for the nestlings to exit when they mature. A 1 1/2" entrance hole is the correct diameter for the Eastern Bluebird and Western Bluebird, 1 9/16" diameter for the Mountain Bluebird.