Bluebird Box Styles
There are 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 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.
Eastern Bluebird: 4″ x 4″ or 5″ x 5″ , or 4″ in diameter for circular boxes. Peterson style boxes may be slightly smaller.
- 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.
Above is the traditional North American Bluebird Society style bluebird box. It remains an effective and popular choice. It is an easy and inexpensive house to make yourself. This version has an extension on the entry hole to provide predator protection.
The slant-fronted “Peterson” style box, below, has become popular in many areas. Some research suggests house sparrows seem to avoid the oval-shaped hole while starlings do not like the smaller internal nest size.
PVC bluebird houses are easy to build, just make sure your design allows easy access to the inside of the nest box. Some reports indicate that house sparrows are less found of PVC houses than they are of more traditional designs.