Educate yourself first. Don’t make the mistake of buying or building a martin house before thoroughly researching the subject. You may find out after investing money, time, and hard work, that your yard is too tree enclosed for martins, or your martin house is difficult or impossible to manage. There are many sources of information available. Visit www.purplemartin.org, the PMCA’s web site, talk with other landlords, and read “Enjoying Purple Martins More” and/or Stokes’ Purple Martin Book. PMCA members can benefit from all the current information published in the colorful Purple Martin Update magazine.
Choose the right location. One of the major reasons people fail to attract martins is that they place the martin housing incorrectly. Martins have very specific space requirements. Their housing should be in the center of the largest open spot available, about 30-120 feet from human housing. Place the housing where you can see it so you can enjoy watching and hearing the martins. There should be no trees within 40 feet, preferably 60 feet. In the southern half of their breeding range, martins are less fussy about house placement, so sometimes housing can be within 25 feet of trees and still attract martins. But the farther housing is placed from trees, the better. Housing height should be about 10-15 feet. Don’t attach wires to the house or pole, especially if they lead to trees, buildings, or the ground. Predators can use the wires to access the housing.
Put up manageable housing. Your chances for success will be better if your housing is easy to manage. Choose a pole that telescopes, or is equipped with a winch or lanyard, and housing that has easy access to compartments. Avoid housing that only allows access by removing the roof, or layers of the house, or through entrance holes. Paint houses and gourds white, or a light color. White housing attract martins best, and reflects sunlight, keeping nestlings cooler. Compartment floor dimensions should be at least 6" x 6," but larger compartments (7" x 12") are preferred by the martins, and offer better protection from predators and rain. Larger compartments are also attractive to European Starlings, but a special entrance hole will minimize starling problems. Height of compartments can be 6" or 7." Place entrance holes 1" above the floor. An entrance hole of 2&1/8" is preferred by the martins, but they will use a range from 1&7/8" to 2&1/4." Make sure there is adequate ventilation and drainage in each compartment. Many plans for martin housing, and some manufactured houses, are made to incorrect dimensions, so if your housing is unsuccessful, check the dimensions and modify where necessary. Most houses can be improved. Add insulation to the attic, remodel interiors to offer double-size compartments, and add porch dividers. Dividers help keep males from claiming extra compartments, and can double occupancy rates. They also keep nestlings from wandering to other compartments, where they can get lost and die, or steal food from younger nestlings, causing them to starve.
Protect your housing from predators. Don’t assume that because you never see any predators there are none around. Raccoons, snakes, and owls raid bird houses at night. Few experiences are more painful than losing all your martins because you didn't equip your poles and housing with guards. Whether your housing consists of 6" x 6" or 7" x 12" compartments, external guards to protect against owls, hawks, and crows are insurance every house needs. Since all martin poles, wood or metal, are easily climbed by rat snakes, squirrels, and raccoons, all birdhouse poles require climbing animal barriers. You can install guards before or after your martins have arrived. In areas with fire ants, Teflon spray or tape, or a ring of grease on the pole, will stop the ants. Grease won't stop snakes or raccoons, so install a pole guard, too.
Open housing at the right time, and don't close it too soon. Adult martins are rarely attracted to new breeding sites — they return to the sites where they bred previously. Typically, it is subadult martins (last year’s young) that colonize new sites, and they begin arriving about 4 weeks after the first adults. At new sites, opening housing when the “scouts” are due decreases chances of attracting martins by giving House Sparrows and starlings 4 weeks to claim the site before the subadult martins arrive. To improve your chances, keep housing closed until it's time for subadults to arrive. At active sites, the first martins usually show up within a week or two of previous years’ arrival dates. Have your housing ready, but keep it closed until some martins return. Migration is a drawn-out affair, with martins arriving for 8-12 weeks in the north, 16-20 weeks in the south. Martins can arrive and begin nesting up through the end of June, so keep your housing ready; don't close it up, or let other birds use it.
Practice active management by controlling House Sparrows and European Starlings. Starlings and House Sparrows will take over compartments, destroy eggs, kill nestlings, and prevent martins from nesting at unestablished sites. Adult martins are often injured or killed by starlings. Successful martin landlords do not tolerate these nonnative nest-site competitors. Starlings and House Sparrows are not protected (since they are not native birds) and may be controlled by trapping, shooting, and nest tear-outs. You can also use the starling-resistant entrances pictured here. If native birds (Tree Swallows, wrens, bluebirds, or flycatchers) try to nest in your martin housing, close it and put up single-unit boxes for these desirable species elsewhere on your property. Reopen the martin housing only after the new box has been accepted.
Conduct weekly nest checks, daily walk-unders, and keep written records. Although many landlords are reluctant to lower their housing during the breeding season to peek in on their tenants, it's one of the most valuable practices landlords can adopt. Nest checks will not cause martins to abandon their young. If your martin housing raises and lowers vertically, as it should, number the compartments, check nests weekly, and keep written records. Landlords who conduct regular nest checks will be more successful, simply because they’ll discover any problems that occur in time to correct them. In addition to weekly checks, walk under the housing daily to look for plucked martin feathers, thrown-out nestlings, dropped insect prey, hatched eggshells, etc. The items you find are clues to what's going on and may alert you to problems that need attention.
Keep your martin housing in good repair. Remove nests and scrub housing with a 10% bleach solution (1 part bleach to 9 parts water) in the fall. Rinse and air dry before storing or closing for the winter. Take care of any needed repairs now, so you won't be caught unprepared next spring. Wooden houses and natural gourds need to be sanded and repainted periodically. All types of housing will last longer if stored indoors over the winter. If housing is left out, plug the holes, otherwise House Sparrows and starlings will claim it in late winter and be impossible to dislodge come spring.
Be prepared for problems: Keep the phone number of a licensed wildlife rehabilitator handy; a rehabber is a sick or injured bird's best chance for survival. Place fallouts back in the nest; if that's not possible, take them to a rehabber. Don't try to raise them yourself; it’s illegal and your good intentions cannot replace the experience and skills of a rehab specialist. If parasites or wet nests threaten the survival of nestlings, replace the nest material with clean, dry wood shavings. Never use pesticides in nest boxes; it's illegal and they are not safe for wild birds and nestlings.
Supply these aids: Crushed, dried eggshell or oystershell is a valuable dietary supplement that supplies calcium and grit, and helps prevent calcium deficiencies in nestlings. Offer it all season in an open feeder. Eggshells should be rinsed, dried thoroughly in the sun or a 350 degree oven, then crushed into small pieces. Landlords can also put nest material out for their birds. Dried pine needles, dry twigs, or a bale of straw scattered in an open area will be used by the martins. Create a supply of mud for them by soaking an area of ground with a hose.
Work with other martin enthusiasts in your community. Martin landlords are a very friendly bunch of people, so don't be shy. Stop and introduce yourself to other landlords, and make some new friends. Ask the local newspaper to do a story on martins, and have meetings to share information. Consider hosting an “open house” at your colony site for those interested in martins. By promoting good management and participation in PMCA research projects, you can help increase martin numbers locally. And, if you can help area landlords become better educated and more involved in management, you’ll assure a better supply of fledglings each season to help martin populations thrive again.
James R. Hill, III & Louise Chambers
Purple Martin Conservation Association
Edinboro University of Pennsylvania
Edinboro, PA 16444