Purple Martins (and Mosquitos)
September 5, 2012
Putting up a Purple Martin house is like installing a miniature neighborhood in your backyard. In the East, dark, glossy-blue males and brown females will peer from the entrances and chirp from the rooftops all summer … Our largest swallows, Purple Martins perform aerial acrobatics to snap up flying insects.
~ All About Birds
The Purple Martin Conservation Association says that Purple Martins (Progne subis) are the largest member of the swallow family in North America, measuring 7 1/2 inches (19 cm) long and weighing 1.9 ounces (55 grams). Of the three races (subspecies), the ones we see in Michigan are Progne subis subis. The PMCA page on Attracting & Managing Purple Martins says:
Purple Martins spend the non-breeding season in Brazil then migrate to North America to nest. East of the Rockies they are totally dependent on human-supplied housing. West of the Rockies and in the deserts they largely nest in their ancestral ways, in abandoned woodpecker nest cavities. In the Pacific northwest, Martins are beginning to use gourds and clusters of single-unit boxes for nesting.
The pair-bond of the Purple Martin is monogamous. The male and female cooperate equally in building the nest out of mud, grass and twigs. The female lays two to seven pure-white eggs at a rate of one egg per day. The female incubates the clutch for approximately fifteen days, then the young hatch. The parents both feed the young continuously for a period of 26-32 days until the young fledge. The young continue to be dependent on their parents for food and training for an additional one to two weeks after fledging. It’s not uncommon for the fledglings to return to their human-supplied housing at night to sleep during this period. (Click to see an animation of the growth of a nestling purple martin.)
Martins, like all swallows, are aerial insectivores. They eat only flying insects, which they catch in flight. Their diet is diverse, including dragonflies, damselflies, flies, midges, mayflies, stinkbugs, leafhoppers, Japanese beetles, June bugs, butterflies, moths, grasshoppers, cicadas, bees, wasps, flying ants, and ballooning spiders. Martins are not, however, prodigious consumers of mosquitoes as is so often claimed by companies that manufacture martin housing. An intensive 7-year diet study conducted at PMCA headquarters in Edinboro, PA, failed to find a single mosquito among the 500 diet samples collected from parent martins bringing beakfuls of insects to their young. The samples were collected from martins during all hours of the day, all season long, and in numerous habitats, including mosquito-infested ones. Purple Martins and freshwater mosquitoes rarely ever cross paths. Martins are daytime feeders, and feed high in the sky; mosquitoes, on the other hand, stay low in damp places during daylight hours, or only come out at night.
While it sounds like purple martins aren’t the mosquito machine that they’re sometimes billed as, it does sound like they’d make a great addition to your yard! Read on to learn about all kinds of things you can do to make your martin house a home. Also check out their songs page and get a lot more info and photos from the All About Birds Purple Martin page.