Mancuso - Building purple martin houses

Janice Therese Mancuso

In the eastern part of North America, Purple Martins rely almost entirely on human-supplied housing for nesting sites. Many believe that the unique relationship between Purple Martins and humans was established in the southeastern United States with early Native Americans. Many tribes in that region used hollow gourds to dip water from ponds and then hung the gourds to dry in the sun and the drying gourds became perfect homes for the cavity-nesting birds. The Native Americans welcomed the Purple Martins to their community, finding that the friendly birds not only helped to control insects but also mobbed and harassed other birds and small animals that were attracted to drying meats and hides. They hung out additional gourds to entice more martins to live with them. Martins soon preferred these easily obtainable nesting sites and the safety from predators that nesting near humans rather than in abandoned woodpecker cavities or rock crevices provided. Also, the gourds roomy nesting chambers permitted more eggs to be laid, and the community housing gave each male martin the opportunity to mate with more than one female, adding genetic diversity to their off-spring.

Hollow gourds are among the favorite nesting sites

As time passed, other tribes began to hang gourds to attract the birds, and more and more Purple Martins chose gourds over natural cavities. Early American settlers and plantation slaves followed the Native Americans custom, experimenting with ceramic gourds and wooden houses. Each year the martins would return to these nesting sites, and the keepers of the sites became known as landlords. By the early 20th century, eastern Purple Martins were almost entirely dependent on human-supplied housing.

Purple Martins have a large, devoted following a following willing to spend almost $30 million annually on housing and related merchandise. In some areas the Purple Martin population is declining, and since the birds rely on human-supplied housing, if this housing isnt provided, the species will perish. But a Purple Martin colony requires a lot of time, attention, and most important commitment, so before you decide to start one, you must learn all you can about the birds and their needs.

Identifying Purple Martins

Purple Martins, the largest members of the swallow family in North America, are divided into three subspecies. Progne subis subis breed in the eastern part of North America and are the most abundant. These people-friendly birds nest in multicompartment housing and have been managed by humans longer than any other species in North America. Progne subis arboricola breed at high elevations along the Pacific Coast as far north as British Columbia, extending east to the Rocky Mountains and some parts of Canada. They live singly in natural cavities but can be attracted to single houses and gourds. Progne subis hesparia, the smallest subspecies, live in the Sonoran Desert of the southwestern United States and northern Mexico as well as the arid Baja peninsula. They make their home in cool interior cavities of saguaro cacti and are not imprinted on using man-made houses.

Purple Martins range in size from 7 to 8 inches (17.720.2 cm), with a wingspan of 12 inches (30.4 cm). Their long, narrow wings allow them to spend much of their time flying, including soaring and performing aerial acrobatics. When not in flight, they like to perch on whatever is available especially utility lines or on the poles of their housing colonies.

Adults acquire their full color by the third summer. Adult males have a blue-black plumage that reflects purplish in sunlight (hence the species popular name). Adult females have a gray throat and breast, purple crown and back, black wings and tail, and white/gray undertail coverts. Both the male and female subadults are similar in color to adult females, though the male has darker patches on his throat and around the eyes and patches of purple feathers on his breast and belly, and the female is slightly lighter than the adult female and has white undertail coverts.

The female Purple Martin (left) has a light-colored underbelly while the male (right) is completely blue-black.

Each year, Purple Martins migrate from their wintering grounds in South America to the United States and Canada to breed. The first birds begin arriving in southern Florida in mid-January; migrating martins gradually make their way north, eventually reaching Canada by early May.

Each spring, thousands of landlords look forward to the arrival of the Purple Martins. Martins are one of the first species of neo-tropical migrating birds (birds that overwinter in the tropics) to reappear, and many people consider their arrival to be a sign to begin planting crops. As the birds return, landlords know that the next few months will bring the pleasure of observing the birds during courtship and nest building, then of monitoring the nestlings until they fledge. Mating, breeding, and raising offspring are accomplished only when housing and territory have been secured, so early arrivals (the so-called scouts) have first choice at nesting sites and can get a head start on the mating process.

When their young have fledged, Purple Martins migrate back to South America. In the most southern parts of the United States, the birds may start their journey as early as June. In the northern states and in Canada, migration may not begin until August.

Before migration begins, however, martins often gather at neighboring colonies, arriving and leaving in small, loose groups but combining into large even huge flocks to roost at night. In the south along the Gulf Coast, flocks contain hundreds of thousands of birds from all over the United States, including southern birds that have finished nesting and are heading south as well as late-arriving subadult birds heading north. The birds tend to gather near water (where food, in the form of insects, is abundant) on utility wires, antennas, or trees and will bathe, groom, and feed. Before dusk theyll fly to another location to roost for the night.

The state of So Paulo, in Brazil, is a popular migration destination for many Purple Martins. Many martins also spend the winter in sections of Bolivia, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Suriname, and Venezuela. Come spring, they once again trek thousands of miles back to North America to breed and start the life cycle anew.

Major Martin Roosts

If mid-June to mid-July finds you in the area, two roosts in the southern United States are worth a visit.

Lake Pontchartrain Causeway, Louisiana: This 24-mile causeway has two roosts. The northern end includes local breeders plus migrating birds; the southern end is believed to be just local breeders. As many as 250,000 Purple Martins can be seen from mid-June to mid-July. More information can be obtained from the National Wildbird Refuge Web site at www.gnofn.org/~swallow/.

Lunch Island, Lake Murray, South Carolina: The Columbia Audubon Society and two other groups combined efforts to make this roosting area a sanctuary. They estimate that in mid-July 750,000 Purple Martins roost on 12-acre Lunch Island, which is best observed from a boat. For more information about Lake Murray and the surrounding area, visit the Lake Murray Web site at www.lakemurray.com/lake.htm.