Purple martins are colonial and prefer large birdhouses or gourd racks with multiple compartments. To attract martins, martin houses should be placed in the center of the most open area available, at least 30 feet from human housing and at least 40 feet from trees taller than the martin housing.
Purple martins are the largest North American swallows. They eat only flying insects that they catch in flight, so landowners hoping to attract them should avoid using insecticides. Bird feeders do not attract martins, but establishing places where the birds can obtain fine grit for their digestion or crushed eggshells to supplement their calcium needs during nesting may encourage them to stay. Purple martins also need open water sources that allow them to scoop up a drink on the wing. If a natural water source is not available, an elongated water feature is better than a simple birdbath.
Martin houses should be 10 to 20 feet above the ground on a support equipped with pole guards to prevent predators from climbing to the nests. A telescoping pole is convenient so that the landowner can bring the house down to eye level regularly and check for sparrows or starlings that compete with the martins for nesting space. At sites without existing martin colonies, a landowner can put up martin housing as soon as the first scouts of the migration appear in the spring and continue attempts to attract martins through the end of June.