Purple martins are aerial insectivores, which means they eat insects while in flight. Obviously it is easier for a purple martin to catch flying insects in an area that has few trees. For this reason, people who live in areas with large open lawns, fields or pastures, or ponds and lakes are more likely to attract martins.
Purple martin housing works best when placed 10 to 20 feet in the air. One of the most important requirements of purple martin housing is the ability to raise and lower the house. Other bird species, especially non-natives (starlings), may take up residence in your martin house. If this happens you can lower the house and remove the nests.
Studies of different types of martin housing resulted in the following recommendations. Gourds are clearly the most productive in larger clutch size and number of fledglings; second were wooden houses; and the least productive type of housing was aluminum. Regardless of the housing design, the floor dimensions for each compartment should be a minimum of 6" X 6". Larger compartments (7" X 12") are preferred and also provide increased shelter and protection from rain and predators. Entrance holes should be placed 1" above the floor and be 2 1/8" in diameter.
