The three wren houses shown here may be used as the hanging type or placed on a post. Build them using these free woodworking plans.
This article describes how to create a bluebird house that is easy to make and costs very little. You can use it as a youth project, or you can assemble them yourself and put them around your property if you are interested in attracting bluebirds.
We can build artificial cavities to improve the availability of nesting space. This activity describes how you can build a simple, but effective bird nest box, designed to attract bluebirds, chickadees, swallows and wrens.