Unlike some birding activities, the key to attracting a purple martin population year after year does not lie in providing the right food. Purple martins feed exclusively on flying insects and do not visit bird feeders. Purple martins depend on human-provided housing east of the Rockies and are very specific about their habitat needs.
Place the martin house in the most open spot on your property. These swallows catch their prey on the fly and need room to perform their aerial acrobatics. There should be no trees or dwellings within 40 feet of the martin house.
Elevate the martin house on a pole between 10 and 20 feet high. Keep vines or wires away from the house, as this allows easy access to predators such as raccoons and snakes.
Paint the purple martin house white or a pastel color. White reflects the heat of the sun, preventing sensitive nestlings from becoming overheated.
Control competition for the martin house from aggressive house sparrows and starlings. The best way to reduce competing birds is to use a house with exacting entry hole dimensions. The hole should be placed ½ inch or less from the floor of the house and the height of the hole must be exactly 1 3/16 inch tall.
Remove the nesting materials of competing birds should the house be claimed by bluebirds or other swallow species. Use a housing unit with a telescoping pole to make clean-outs easier.
Check the martin housing frequently for signs of parasites or predation. Purple martins are not bothered by these checks. If you see signs of these problems, install owl guards or replace nests with wood shavings as needed.
Store the purple martin house indoors during the winter, when the birds migrate to Brazil. This prevents wasps or other pests from colonizing the house. Put the house out when you see the first martins arrive in the spring, which varies from March to June depending on your location.