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THE PURPLE MARTIN - A MOST
WANTED BIRD Nature, with great wisdom and a sense of balance, has populated our earth with a great variety of wild birds. To reduce competition, entire groups of birds have become very specialized in their food preferences. For example, sparrows are seed-eating birds that help control prolific growth and spread of weeds. There are birds that search for and destroy myriads of aphids, grubs, and beetles on the ground and in shrubs and trees. Swallows are very specialized and feed only on flying insects caught while on the wing. Fortunately, swallows arrive each spring just at the time flying insects first take wing before the majority of insects have had an opportunity to lay eggs. Without swallows, we would be quickly inundated by hordes of insect pests. Almost every species of bird is of inestimable benefit to man, but too often little thought is given to the needs of birds. At times, humans have relentlessly destroyed the habitats necessary to sustain a species. Increasing populations of many declining species can be encouraged by reestablishing habitat. Modern farming methods and expansion of cities, towns, and urban areas have efficiently cleared away dead trees, thus eliminating natural nesting sites for several cavity nesting birds including one of "America's most wanted birds", the purple martin (Progne subis). The purple martin has had many obstacles to overcome in addition to the disappearance of natural nesting sites. One is competition from the imported house sparrow (Passer domesticus) and European starling (Sturnus vulgaris). Purple martins are also vulnerable to weather. Cold weather in the spring (around mid-March) in the central Tennessee area can curtail the flying insect supply so drastically that the bird may starve in two or three days. Hot weather also kills thousands of young birds before they can successfully leave their oven-like nests. Mites and other parasites also take a toll on the young martins. Pesticides have killed thousands of these birds, and the ever-present natural predators such as cats, raccoons, snakes, and owls stalk the martin. Purple martins, the largest member of the swallow family in North America, are migratory birds that spend winter months in Brazil. Migration to North America occurs in spring, with martins usually arriving in central Tennessee in early to mid-March. Nesting takes place throughout most of the United States and southern Canada during summer. Purple martins are not extremely selective eaters. Because of their amazing capacity to consume larger flying insects, including dragonflies, beetles, locusts, weevils, moths, house flies, horse flies, and deer flies, martins make any neighborhood they colonize more pleasant. The martin's digestive process and metabolic rate are extremely rapid, and it must consume its own weight in insects each day. The average weight for a purple martin is about four ounces, which is equal to about 14,000 mosquitoes or that equivalent in other insects. The martin's short, triangular beak opens into a somewhat large "scoop" as it darts through the air, snatching large insects that are trapped by a sticky coating inside the mouth. Smaller insects are compressed into a ball and returned to the nest to feed the young. Male martins are uniformly blue-black above and below; no other swallow is black-bellied. The female is light-bellied with a grayish throat and breast and dark gray back. Martins glide in circles with alternating quick wing flaps and glides and will often spread the tail feathers. Martins seem to have a genuine affection for humans and often will colonize more quickly in locations where there is considerable human activity. So what better place is there to encourage the start of a colony of these birds than near your own home? This particular area of central Tennessee has several thousand purple martins, and they can usually be attracted to your home if certain criteria can be met. Becoming landlord to them sometimes takes a lot of patience. New houses usually stand empty the first season, one pair may use it the next, and perhaps three or four pair the third year. After that, the colony can and usually does "snowball." However, certain guidelines must be followed to accomplish the goal of providing a suitable place for these birds. Understanding these guidelines will probably mean the difference between success or failure. The earliest known man-made martin houses were provided by Native Americans. These houses were nothing more than hollow gourds suspended from poles near tepees. Gourds are still used today. However, they are very porous and perfect for harboring parasites. They're hard to clean as each must be taken down individually and old nesting material removed through the entrance hole. Gourds can also become miniature ovens and literally "cook" the young birds. If young birds seek the coolness outside the gourd, there's nothing to prevent them from falling to the ground. They then die from starvation or are consumed by predators. During the 17th and 18th centuries, Europeans began colonizing this continent. These people, with considerable carpentry skills, built wooden martin houses. Most wooden houses built today still offer some of the same problems as the gourd. Also, with the introduction and following explosion of the house sparrow and European starling populations, the gourd and wooden martin houses became very attractive to these nuisance birds. Superior houses such as gourds made of fiberglass and aluminum houses, which are both easy to maintain and very effective in increasing purple martin colonies, can now be purchased. Both types of housing are also lightweight. Excellent plans for good houses are also available for those who wish to construct their own box.
Consider three basic factors when setting up your purple martin system: the house, the pole, and the location. First, the house should: be lightweight, cool, attractive, durable, and parasite resistant; be equipped with guardrails to protect baby birds from falling; be equipped to clean each compartment without disturbing others; have a means to plug holes during winter; have bright interiors to discourage sparrows and starlings; have proper ventilation and drainage; and finally, have a pole between 12 and 15 feet tall that allows the house to be readily raised and lowered (preferably vertically) without disturbing nests. Compartment sizes should be 6" x 6" x 6". Smaller compartments can cramp the birds; larger is fine but adds weight to the house. Openings should be 2-1/8 inches in diameter. The more compartments offered, the better your chances of attracting the birds. Six compartments per house is the minimum for the best start. Martin houses should be arranged to complement your landscaping scheme and for the most desirable view of the compartments from your home or lawn recreation area. Arrange the house to align the most openings away from prevailing winds in your area. Houses should be placed at least 15 feet from any trees or buildings. Martins seem to prefer lots of free flight area for soaring into the house. Water in the form of ponds, creeks, lakes, etc., located close by is desirable because a martin incorporates mud into the nest. One problem should be reiterated. House sparrows and European starlings are very gregarious and aggressive birds, especially when in competition for nesting cavities. The purple martin will not challenge these competitive characters and will most often be chased from the nest houses. Even if house sparrows or European starlings share a house with martins, the mites which the undesirable birds carry can completely eliminate a martin colony. If house sparrows or European starlings move into a house, remove the nesting material and burn it. If you don't, they'll put it right back. A pair of house sparrows can build a nest and lay one egg in less than eight hours. By late February you should have your martin house erected on a suitable pole in an open area. Now what? Putting out bits of eggshell will help attract martins. Dry them in an oven, break into pieces no larger than a fingernail, and place them on some type of elevated platform out of the reach of predators. Egg shells provide martins with minerals they may not get from a regular diet of insects. Another tip for attracting martins, especially in urban areas or during dry periods in all locations, is to place small sticks, straw, and short pieces of string on the ground near the house. Then make a mud puddle for the martins in an open area by taking off about two inches of sod in a 2' x 3' area. Save the sod for later replacement. Keep the exposed area soaked with water for nest building. The martins will love it. For more information concerning the natural history of “America’s most wanted bird”, visit http://www.purplemartin.org.
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