Wild birds possess the ability to find their own nesting sites, be they in trees or shrubs, a rooftop crevice, or a hanging flower basket. While many species also nest in artificial birdhouses, the Purple Martin relies totally on humans to supply its nesting sites.
Human attempts to attract the Purple Martin have caused a "tradition shift" in its nesting habits. Originally, Purple Martins nested in old woodpecker holes or natural tree cavities. Preferring communal dwelling, numerous pairs of martins lived in close proximity to each other. However, when Native Americans discovered that Purple Martins liked nesting in hollowed-out gourds they began hanging them in their villages to attract the birds. When the first European colonists came to North America in the 1600s, they, too, began providing nesting sites for martins. Eventually they offered the birds ceramic pots and then wooden houses in which to nest. By the 1860s, nearly every farm, plantation, and slave quarter had an active martin house.
As many North American forests were cut down for lumber or to provide farmland and housing communities, the woodpecker holes and natural tree cavities previously used by the martins as nesting sites disappeared. The birds began to rely on artificial houses to an ever greater extent. Today, they nest only in martin houses erected by humans.
The introduction of the House Sparrow in 1851 and the European sparrow in 1890, two species that rapidly spread across North America, caused the local extinction of martins in some areas. These birds aggressively drove the Purple Martins out of their artificial homes — and then usurped them. Thus, martins had fewer places in which to breed, and their numbers began to decline.
In 1996, the U.S. Fish and Wildlife Service released a 20-year study showing that the numbers of Purple Martins north of the Mason-Dixon Line had decreased during the research period.
Since then, the U.S. Fish and Wildlife Service has deemed the Purple Martin a "bird of special concern." According to Terry Anne Suchma, executive director of the Purple Martin Society, N.A., in Burr Ridge, Illinois, the reason for this designation is threefold. "First, the Purple Martin is completely dependent upon humans, east of the Rocky Mountains, to supply the birdhouse for it to nest and breed," says Suchma. "Second, these birds are weather sensitive. Many arrive too early, and if we have cold spells and snow they starve to death. Third, they are specialized eaters. They don’t eat from bird feeders. They only eat flying insects they catch in the air."
Like many other birds, the Purple Martin winters in South America and then migrates northward along the Mississippi River as far north as Canada to nest and breed in early spring. Thus, Illinois and Wisconsin have abundant populations of martins each spring and summer.
"Scouts," older birds who migrate four to eight weeks before the younger birds, arrive in our region in late March or early April. They return to the places they have successfully nested in the past. Those hatched and fledged from area nests the previous year arrive later and start new colonies.
Purple Martins like houses with a minimum of eight compartments mounted on poles 10 feet high or more. They prefer to be at least 40 feet away from trees but no more than 100 feet from a house.
Since martins do all their eating, drinking and bathing on the wing, they rarely land on the ground. The best time to see these birds is when they are nesting or tending their young. At these times they land to pick up and deliver nesting materials, feed their young, or preen themselves atop their houses.
Purple Martins grow to about eight inches in length with a wing span of a foot. The adult male sports a glossy, iridescent blue black color. Females are the same size but have a grayish whitish underbelly, while adult males lack this feature. Young males and females also have lighter color under parts. They finish breeding in late July, at which time they begin pre-migratory flocking. Fifty years ago, Chicago bird watchers would see hundreds of thousands of martins converging on the Lake Michigan shore to eat the plentiful insects, such as flying ants, dragon flies, beetles, houseflies, wasps, and midges. "It was like a black cloud over Montrose Harbor," says Suchma. Chicago still experiences a huge staging of Purple Martins in the fall, and, reports Suchma, "When the martins are done eating, they fly down to Belmont Harbor and roost in the trees." By mid-September, however, they have all migrated southward.
Many martin house manufacturers encourage bird lovers to start Purple Martin colonies under the premise that these birds decrease the mosquito population. In fact, this pest represents only three percent of a martin’s diet (They also eat wasps, flies, and other bugs.). In any case, more valid reasons for attracting this bird into your yard abound. According to Ken Kostka, research assistant at the Purple Martin Conservation Association in Edinboro, PA, "Martins are very graceful, very friendly, and their vocalizations are pretty or soothing. They have a bubbly chatter. We like to say they are just great to have around.
"Purple Martins know people are not their enemies...they know they are safer when they are close to a human dwelling."
Bird lovers who want to start a Purple Martin colony should purchase at least an eight-compartment house with ten by twelve-inch cavities and a rope and pulley system to raise and lower the house for nest inspections. According to Suchma, when you become a Purple Martin colony’s "landlord" you become an "amateur wildlife manager." In other words, it becomes your responsibility to ensure their houses are free of starlings and sparrows and that predators do not endanger them. If you do this successfully, the martins will return to your yard for many years to come.