There are many different designs of bluebird boxes and each one has its supporters. Almost any style will do but boxes that conform to the following guidelines are most likely to be successful.
Styles and sizes
Commercially produced boxes are available in a variety of designs and styles. Look for houses that have been approved by the North American Bluebird Society. If the nest box does not have NABS approval, then check for the following dimensions.
Eastern Bluebird: 1 1/2 inch round holes, 1 3/8 x 2 1/4 inch vertical oval holes, or 1 1/8 inch horizontal slot entrances.
Western or Mountain Bluebird: 1 9/16 inch round opening.
Where ranges overlap, use a 1 9/16 inch round opening.
Eastern Bluebird: 4″ x 4″ or 5″ x 5″ , or 4″ in diameter for circular boxes. Peterson style boxes may be slightly smaller.
Western or Mountain Bluebird: 5″ x 5″ or 5 1/2″ x 5 1/2″
- A design with a 5 in. front overhang will discourage predators from accessing the nesting area from above.
- Boxes should be watertight but have good ventilation.
- Boxes should be easy to open and close to allow for easy checking of the nest and removal of old nesting material.
These are several of the more popular styles of bluebird boxes.