Pasture land with scattered trees or a large, open yard at least an acre in size with a water source nearby . . . if this describes your property, it’s likely you can attract bluebirds. Bluebirds were common when much of rural Iowa had pastures, but changes in livestock agriculture have reduced drastically the habitat available for this popular songbird.
Modern acreages are again providing the open, short grass habitats preferred by bluebirds. Natural cavities for nesting often are scarce, but landowners can easily build houses that provide suitable space and help protect bluebirds from predators such as cats, raccoons and snakes.
Simple Bluebird House Plan
Houses range from simple to complex, and plans often are available from your local Extension office. You can make a simple box from a 1"x 6" x 6' board. Rough cut western cedar is very durable, but clear pine will do. Avoid plywood if squirrels or deer mice are common because they will gnaw on it.
Cut the board in the following dimensions: the back, 13.5 inches; the roof, 7.5 inches; the front, 9 inches; two sides, 9 inches; and the floor, 4 inches. Assemble the box with galvanized nails or screws. The floor should be recessed slightly into the bottom. The roof should be flush at the back and extend over the front. One side will serve as the cleanout door, hinged at the bottom to open from the top out. A simple hinge consists of nails driven opposite each other through the front and back at the bottom edge. A single nail inserted in a downward slanting hole through the front of the box will lock the side cleanout door in place.
Drill several quarter-inch drain holes through the bottom. Drill similar-sized vent holes in the sides just below the roof line. The entry hole should be 1.5 inches in diameter and centered at least 5 inches above the floor.
Assemble the box with the rough side in if using cedar, or make shallow saw cuts on the inside of the front (below the hole) if using smooth lumber. The roughness helps young birds or weak adults get out. Do not add a perch peg. Bluebirds don’t need it, and house sparrows and wrens will use it to harass your preferred tenants. Mount the box 5 feet above ground, away from brushy areas and ideally facing a nearby tree. Boxes mounted on fences (regular steel posts) are too easy for predators to reach. PVC plastic pipe slipped over a steel fence post and positioned away from the fence makes it difficult for climbing predators to reach.
Have your box in place by early March, when male bluebirds look for nesting territories. Bluebirds usually nest twice per season, so additional boxes mounted a few hundred feet apart often will be used. Monitor your box at least weekly through mid-summer to remove unwanted house sparrow and wren nest material. Without your help, these two species will drive bluebirds away.