East of the Rockies, martins are totally dependent on humans to provide houses for nesting.
Rooms for rent
To attract a houseful of purple martins, pick the right location and follow some tried and true tenets.
Kathryn A. Kahler
To attract new tenants, most landlords do nothing more than run an ad in the local paper or put up a "for rent" sign in the window. If you're trying to attract a nesting colony of purple martins, it's another matter entirely.
Just ask Westfield biology teacher Brian Thays who admits he's hooked and somewhat of a "nerd" about attracting martins. When he was 10 years old, Thays would bike several miles to see established colonies near his home. It sparked a passionate pursuit to attract purple martins to his property.
"I'm actually pretty new to the hobby," admits Thays, who has had martins nesting in his T-14 style martin house for two years. "But once you've seen these beautiful birds with their wonderful swooping, gliding flight pattern literally dive out of the sky to your bird house, you're hooked. I want to get the message out so others don't end up making some common mistakes that leave their bird houses empty, or worse, full of non-native house sparrows or European starlings," he says.
Purple martins are the largest North American swallows. Adult males are about 7½ inches long with iridescent purple-black plumage front and back. The dimorphic females have similar coloring on their backs but have a dingy grayish breast. Martins winter in South America and migrate back to their breeding grounds in North America in the spring sending scouts that reach Wisconsin in early to mid-April. Breeding pairs are monogamous and once they choose a nesting site will come back to it year after year as long as they don't experience nest failure.
East of the Rockies, martins are totally dependent on humans to provide houses for nesting. Oldest adults arrive first; subadults return a month or more after adults.
Martins eat only flying insects on the wing and don't specialize in any one species, taking a variety of beetles, flies, bees, wasps, dragonflies, butterflies, moths, cicadas and others. Despite common belief, they eat very few mosquitoes, probably because martins feed higher in the sky than mosquitoes tend to fly. Extensive studies of the stomach contents of martins show that mosquitoes make up less than 3 percent of their diet.
Some of the biggest threats to purple martins are those posed by house sparrows and European starlings over battles for decent nest sites. Would-be martin landlords must be willing and ready to deal with the aggressive competitors or they will likely fail in their attempts to attract martins. Starlings will kill adult martins, their young and eggs. Sparrows will peck holes in the eggs or build their own nests on top of the martin nest, starving the hatchlings. Martin landlords employ techniques such as trapping and euthanizing the nonprotected exotics, relentlessly destroying their nests found in martin houses, or using houses with special crescent-shaped starling resistant entrance holes.
Trapping and releasing birds is not effective because sparrows and starlings will return within hours.
Enthusiasts interested in attracting birds to their martin house can employ a number of "social attraction" techniques to entice new breeders. Martins are colonial nesters and unlike most other birds, prefer to nest in close proximity to each other. That's why methods like setting up decoys, broadcasting vocalizations – "dawn song" and "daytime chatter" are Thays' favorites – constructing fake nests or duct-taping mirrors to nest openings all help in tricking martins into thinking there are other martins around.
"Martins have evolved over thousands of years to feel that if they're close to humans and other martins, they'll have a sense of safety," said Thays. "That's the illusion we try to give."
Despite the pitfalls faced by martin landlords, Thays believes the many benefits of living with purple martins far outweigh the difficulties.
"I really only spend five or 10 minutes a day monitoring my colony now that it‘s established," he estimated. "There are other things you must do on a weekly basis, like lowering the house to check for parasites and predation, and on an annual basis, like fall cleaning and plugging the holes for the winter. The top thing on my list is placement of the house. It has to be 40 to 60 feet away from trees that may provide cover for aerial predators like hawks and owls."
Another item that's high on Thays' list is talking to successful martin landlords to see what has worked for them. Thays volunteers as a landlord mentor in Wisconsin for the Purple Martin Conservation Association, a nonprofit organization headquartered in Erie, Penn. He recommends that anybody interested in becoming a purple martin landlord check out their website (purplemartin.org) for an incredible amount of information. Thays would also be happy to help prospective landlords who can contact him at (608) 296-1684, or by email at Brian Thays.
Kathryn A. Kahler scouts out nest sites and does her bird watching from Madison.