The purple martin is one of the earliest neo-tropical birds to return to the United States each year. After spending approximately five months in South America, purple martins make their appearance in Texas during the first half of February. Sometimes individuals arrive as early as January. These are called scouts. Males usually arrive before the females of their age. The oldest (five-seven years) generally are the first to arrive. These scouts can be seen soaring and swooping high overhead as they search for nesting sites and insects.
The purple martin has been managed intentionally by humans longer than any other North American songbird. Martins are very social birds, but they hate clutter; therefore, martin houses should be built between 10 -15 feet off the ground and, at least, forty feet from trees or structures. They can be made of wood, gourds, plastic, etc. Natural nesting sites include cavities of trees, tree snags, pipe organ cacti, and even between large boulders. Historically, most nesting probably occurred in woodpecker holes in tree hollows.
The purple martin is one of eight species of swallows that occurs in the United States. All members of the swallow family are aerial insectivores. They are the largest of the swallows, weighing approximately 1.75 ounces and having a wingspan of 15 inches. They have broader wings and tails than any of the other swallows. Males do not acquire their adult plumage until their second winter. Females are duller with a sooty gray forehead, gray neck, and grayish underparts.
Martins breed in all but the Trans-Pecos and western third of the Panhandle and South Plains. They do most of their feeding 100-200 feet above ground. Their diet is 100% insects. Martins do devour large quantities of mosquitoes. Most mosquitoes are not available to martins because of their nocturnal and low-flying habits.
Nest construction is a contiguous activity. Once a few pairs begin, many others quickly become active in nest-building. Both sexes construct the nest. Nests are of coarse material, such as twigs, straw, pine needles, or coarse grass. Prior to egg-laying, the nest cup is lined with green leaves. Green leaves are thought to contain a natural insecticide to help reduce parasite numbers or aid in maintaining sufficient moisture for the eggs. The green leaves are added throughout the incubation period. Three to seven eggs are added throughout the sixteen day incubation period.
Males and females are on and off the nest in fifteen minute intervals. The parents feed small insects to the young birds until they fledge at about 28 days. The brood is kept together for one to two weeks, returning to the nest at night or during daytime thunderstorms. After fledging, they return to South America. By the end of September most have left Texas. Ninety percent are believed to winter in and around the state of Sao Paulo, Brazil. Others can be found from Venezuela to Northern Bolivia. Martins can live to be thirteen years old in the wild.
House sparrows and starlings are their worst enemies. Starlings will lay their eggs in the nest and push a martin egg out. The mother martin does not know the difference and will hatch and feed the starling baby as her own. Of course, the starling is much larger and will eat more, sometimes starving the martin babies to death. House sparrows make nests in the martin houses, often destroying the nests and eggs that belong to the martins. Whereas sparrows can raise several broods a year, the martins can have only one. People who have the enjoyment of martin houses also have the responsibility of protecting these special birds from the sparrows and the starlings.