I’ve learned how to build a bluebird house from a naturally hollowed log. In my experience, owners of hollowed logs will often offer up one or two, particularly if they know you plan to use the logs to build homes for birds. I typically use a small chainsaw to cut a number of birdhouses from one long, hollow log.
The interior diameter of the hollow log needs to be 4 to 5 inches so there’s ample room for a nest. Use a hole saw to cut a 1-1⁄2-inch opening 6 inches from the bottom. (Deeper boxes keep nestlings out of reach of predators, and reduce their exposure to the elements.) Attach a roof to the birdhouse at a downward slope so rain doesn’t enter, and enclose and seal the bottom of the hollow log with 3/8-inch plywood and commercial sealant. Drill a few small holes into the floor of the nest for drainage, and a few more holes around the top of the birdhouse (below the roof) for ventilation.
Although they seem shy, bluebirds will often use these houses quite close to human activity. I’ve installed bluebird houses as near as 30 to 40 yards from our country home. We clean the birdhouses by removing the screws that hold the roof in place and then shaking out the contents. These hollow log birdhouses endure the ravages of winter and last at least 10 years.
Norman E. Johnson
Plum City, Wisconsin
Bluebird houses aren’t appropriate for all parts of the United States. The Cornell Lab of Ornithology has created a useful online tool called “Right Bird, Right House” where you can enter your region and habitat to find the ideal bird species for your backyard. Discover your soon-to-be neighbors and download the best predator-proof plan for their humble home at Nest Watch. — MOTHER