Create a birdhouse to attract purple martins.
The opening for a purple martin bird house should be 2 1/2 inches (6.35 centimeters) in diameter. Native Americans were the first to attract the martins to artificial nesting sites by hanging dried gourds from trees. This method remains popular in the southeastern United States today.
As with all martin houses, the nesting box or gourd should be mounted on a pole at least 15 feet (4.5 meters) from any buildings or overhanging branches. Purple martins avoid nests that are vulnerable to climbing predators.
Purple martins like to be near water. They are highly social birds, and they readily accept multiple housing units. In the eastern United States these units are popular structures to attract colonies of birds.