Birdhouses for Purple Martins require appropriate placement and space. The house must be located in the most open available area, at least 30 feet from residential properties. The house needs to be at least 10 feet in the air, the tallest local structure and requires specific paint colors and construction.
When building a birdhouse for Purple Martins, choose a spot in an open area that is 30-120 feet from residential properties. The house must be 10-20 feet in the air and taller than any trees in a 40-60 foot radius. The bird house should be painted white or a very light pastel shade, as a light color will reflect the sun's rays and allow the interior of the house to remain cool. The house's base should measure at least 6 inches by 6 inches, but larger dimensions—7 inches by 12 inches, for example—help to shield against weather and intruders that view Purple Martins as prey. The birdhouse should be 5-7 inches high, and the holes through which the birds enter should be at least an inch from the base. A circumference of 2 1/8 inches is recommended for the entrance holes.
Unfortunately, the birdhouse may attract other birds, squirrels or larger predators. Purple Martin enthusiasts may find it helpful to invest in a pulley system with the ability to raise and lower the birdhouse at will. Lowering the birdhouse makes it more convenient to remove non-Purple Martins and predators or to simply keep an eye on the nestlings.