Particularly, that is, if you are attempting to attract purple martins.
These delightful birds, native to North America, are historically unique because nesting colonies were associated with Native American grower society members who hung gourd houses near their villages.
Many martins winter in São Paulo, a small southern state in Brazil, where nocturnal roosts of 25,000 to 250,000 birds form in town squares. Martins begin returning to North America in early spring. A return trip to southern Oklahoma entails just over a 3,000-mile trip, one way! Northbound martins begin arriving in our area around the last week of February, and arrival dates vary from two to four weeks, depending on the weather. These early birds are often referred to as scouts and were thought to be seeking new or better nesting sites. However, research done by martin enthusiasts at the Purple Martin Conservation Association, affiliated with the Edinboro University of Pennsylvania, has provided contradictory but helpful information for would-be martin landlords. Martin scouts are older adult birds that typically are merely returning to established colonies. Yearling martins, which arrive four to ten weeks after the scouts, are the ones searching for new colony sites.
Many folks attempting to attract martins put up or open the birdhouses in February. The mistake here is that in the interim, before the yearling martins arrive, competing species such as the English house sparrow or European starling take up residence and fend off interested martins. Prospective martin landlords should open the houses about four weeks after the first martins are scheduled to arrive in their area. Martins initiate nesting attempts as late as June, so don't be discouraged if you don't appear to be getting early results.
In the spring of 1996, personnel at the Noble Research Institute Wildlife Unit tried to attract martins by using a multiple-unit, European style, white martin house and quite a bit of house sparrow control. In 1997 the house was moved to a slightly higher, more open area but kept within sparrow-control range of the garage window but still no martins. So 1998 found us armed with the latest advancement in martin housing: two gourds painted white and hung from the now-weathering multi-unit house. We had several midday martin visitors up into June, but no nesting pairs. We expanded the housing to six white gourds, four of which are attached at the top of the television antenna pole, and in 2000 we had seven nesting pairs.
One of the reasons people fail to attract martins is improper housing location. Martin housing should be placed 30 to 100 feet from human's dwellings, in the most open site available, and at least 40 feet from trees that are taller than the martin house. The houses should be placed 10 to 20 feet above the ground.
Timing is a critical component of attracting martins. Many would-be martin landlords open the housing too early, as I said before. Four weeks after the earliest martins arrive in your area is a better time for yearling martin use. Once martins establish nesting colonies, they return year after year to breed.
Competition from other species greatly discourages martins from taking up residency. If native species such as the Eastern bluebird or great crested flycatcher use the martin house, you can persuade them to use other housing by temporarily plugging martin house holes while offering single-unit boxes nearby. Discourage non-native competitors such as the house sparrow or European starling by trapping or shooting them and lowering the house for tearing out nests.
Nest compartments for martins should be at least 6 inches square, but a little larger is even better. White housing is most attractive to martins, and the large birdhouse gourds some are 10 to 12 inches in diameter are hard to beat. Place housing on some type of pole that allows you to check nesting progress and remove the house during winter.
Predation is the most common reason for nest-site abandonment. Nearby shrubs or wires attached to martin house poles facilitate predator access. The black rat snake is incredibly adept at climbing. Use cone or wire mesh predator guards.
By the way, contrary to popular belief, recent food habit studies done on purple martins revealed very few mosquitoes in their diet. They prefer to feed on larger winged insects such as flies, wasps, beetles, and dragonflies.
Purple martins are most enjoyable neighbors and with proper colony management will return to entertain their landlord with delightful song and aerobatic elegance year after year.
The adult purple martin photo in this article is courtesy of James R. Hill III, executive director and founder of the Purple Martin Conservation Association, Edinboro University of Pennsylvania, Edinboro, PA 16444 USA, (814) 734-4420 (phone), (814) 734-5803 (fax), firstname.lastname@example.org (e-mail), www.purplemartin.org.