Adult female and male
One of the favorite birds of people who are not necessarily serious students of other types of bird is the Purple Martin. This friendly fellow returns the affection by preferring to live around humans.
The Purple Martin or Progne subis has been lovingly housed by many for nostalgic reasons -- their grandparents and parents had martin houses. And this bird, for whom everyone watches eagerly in the spring, comes back to his established home year after year.
But the martin is a species which needs humans for a number of reasons. Many factors, such as insecticide spraying, have contributed to a reduction in their number, and martins need our help in removing such deadly threats. Young martins have a high mortality rate more than 75% of fledgling martins die during their first year of life. And 50% of adults die each year. They are particularly vulnerable to bad weather, to starvation, and to extreme heat. They have several natural predators, including snakes, raccoons, cats, squirrels, hawks, and owls, which raid their nests, and competing birds who nest in their houses if given the opportunity particularly House Sparrows and Starlings.
A Purple Martin landlord cannot simply erect a martin house, sit back, and enjoy watching his new colony of graceful birds swooping through the air in pursuit of insects. He or she must diligently fend off the competition and predators, clean out any sparrow nests, clean out the martin nests at the end of the season, and plug the entrance holes for the winter.
If he is undaunted in this role of landlord, the martin will reward his efforts, filling his birdhouses each year with family upon family of this delightful aviary companion and devouring a wide variety of insects flying about his yard.
A Purple Martin will range over an area of about four square miles. He drinks fresh water only, dipping down to catch a drink on the wing. His house may be as close to or as far away from other martin houses as his landlord desires; he has no preference in this matter.
Martins need a source of calcium, and martin lovers may place crushed eggshell or oyster shell nearby for the birds. The eggshell should be washed first to eliminate any bacteria.
Martins may move into a new home the day it is put up, or it may take ten years for them to nest in it.
To attract Purple Martins to a birdhouse, the house should be placed in an open space, at least 40 to 60 feet from any trees taller than it is, preferably within a few hundred feet of human habitation. The birds need a wide space to approach the house from at least two sides, and they seem to know that people will protect them from their natural predators. The activity of people does not seem to bother them at all.
The house should be mounted 10 to 20 feet off the ground, preferably on a telescoping pole so that it can be lowered for easy cleaning and for checking on the young in the nests. A predator guard on the pole is also highly desirable. The house should not be moved, once martins have taken up residence in it, as they will reject it the following year if it is in a new location.
If any other species of bird nests in the martin house before the martins arrive, the house will not attract martins. This may involve frequent, even daily, lowering of the house to evict unwanted tenants, or plugging the entrance holes until the martins arrive.
The houses which are most successful in attracting martins are of a light color. This helps to keep the house cool in the summer's heat and highlights the dark entrance holes. Ventilation holes also keep the birds from perishing on hot days.
The birdhouses should not be opened up until about four weeks after the first martins are scheduled to arrive in the area. The first to arrive, commonly called scouts, are not really scouts, but are merely the oldest martins. Older martins cannot be attracted to new locations, because they have high loyalty to the exact home where they bred in the past. Usually only the previous year's fledglings can be attracted to unestablished sites, and they begin returning to an area about 4 to 5 weeks after the scouts.
Bushes and shrubs growing beneath the martin house should be removed, as this attracts predators such as cats, and martins will avoid the house. Similarly, they will avoid houses which can be reached by squirrels, even by a wire.
A landlord probably cannot have too many martin houses, as most places will support several hundred breeding pairs per square mile. And, while Purple Martins live on flying insects, there is no scientific data to show that mosquitoes form a significant portion of this diet.
A colony of Purple Martins consists merely of more than one breeding pair in a given house. They are not necessarily related to each other.