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The gilbertson bluebird house is a well-known nest box design that was popularized by Steve Gilbertson (MN). Its popularity was due to its simplicity and the success it has had in attracting Bluebirds and other species such as Wrens. The basic box is a 4 inch diameter PVC pipe section, 6 inches long which is capped on one end. The other end is fitted to the front of the box. A 1 1/2” hole is drilled through the cap to allow Bluebirds entry while keeping Starlings and House Sparrows out. A hole in the side of the nest box allows for monitoring of the birds an