Purple Martin Life History

Habitat

Habitat Lakes and PondsPurple Martins forage over towns, cities, parks, open fields, dunes, streams, wet meadows, beaver ponds, and other open areas. In eastern North America they used to breed along forest edges and rivers, where dead snags offered woodpecker holes to nest in. But since humans began supplying nest boxes for them, eastern martins have become urbanites, living almost exclusively near cities and towns. In the West, martins have stuck with woodpecker holes in mountain forests or Pacific lowlands. Purple Martin wintering grounds are savannas and agricultural fields in Bolivia, Brazil, and elsewhere in South America. At night, wintering martins flock into cities and towns to roost, often in the trees of village plazas.Back to top

Food

Food InsectsA year-round insectivore, the Purple Martin eats flying insects at altitudes higher than other swallows, often exceeding 150 feet and sometimes 500 feet or more off the ground. When they encounter prey, they turn suddenly sideways or upward, speed up, and then flare their tails as they trap the insect. Their menu includes beetles, flies, dragonflies, damselflies, leafhoppers, grasshoppers, crickets, butterflies, moths, wasps, bees, caddisflies, spiders, cicadas, termites, and mayflies. They feed during the day, rarely in groups but often in pairs (probably so the male can guard the female from mating with other males). Martins pick up small bits of gravel to help them digest insect exoskeletons.Back to top

Nesting

Nest Placement

Nest CavityBoth males and females visit several cavities before choosing a site (a female chooses her mate largely based on the nest site he occupies). The cavity is usually in a birdhouse, gourd, dead tree, saguaro cactus, building, or cliff, but sometimes in other structures like traffic lights, street lamps, dock pilings, or oil pumps. Birdhouses are variable but most are made of wood or aluminum, contain 8–12 rooms, and hang from wires or sit atop poles in open areas.

Nest Description

Nests in birdhouses, hole in tree, hole in cactus, or crevice in cliff or building. Nest made of twigs, plant stems, mud, and grass.

Nesting Facts
Clutch Size:3-6 eggs
Number of Broods:1-2 broods
Egg Length:0.8-1.1 in (2.1-2.7 cm)
Egg Width:0.6-0.8 in (1.6-1.9 cm)
Incubation Period:15-18 days
Nestling Period:27-36 days
Egg Description:Pure white and smooth.
Condition at Hatching:Weak, with completely bare pink skin.
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Behavior

Behavior Aerial ForagerPurple Martins fly with quick flaps and glides, outlining big circles in the sky as they hunt insects. They rarely land on the ground except to collect nesting material and pick up grit to aid their digestion. Males defend small nesting (but not foraging) territories from other males and females do the same with other females. In eastern populations, each territory includes several compartments within a bird house (and occasionally several bird houses), but most birds gradually give up portions of their territory as more and more males arrive. The female usually defends a smaller territory, which usually shrinks down to the size of its own nest compartment by egg-laying time. Physical fights usually only break out if one bird goes into another bird’s nest compartment. Martins pair up with one male and one female per nest, but sometimes two females may settle into different compartments of one male’s territory. Both sexes frequently mate outside of their pair bond. Adults form flocks as soon as nestlings fledge, and congregate in large roosts throughout the winter. Back to top

Conservation

Conservation Low ConcernPurple Martins are fairly common birds (especially in the Southeast), but their numbers declined by almost 1% per year between 1966 and 2015, resulting in a cumulative decline of 37%, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 7 million with 90% breeding in or migrating through the U.S., 7 % in Mexico, and 3% breeding in Canada. The species rates an 9 out of 20 on the Continental Concern Score. Purple Martin is not on the 2016 State of North America's Birds Watch List. Humans have helped counteract declines somewhat by putting up nest boxes, and people now provide virtually all nest sites for Purple Martins in the East. However, introduced species such as European Starlings and House Sparrows often take over martin houses and injure or kill eggs and nestlings. Purple Martins are also sensitive to cold snaps; bad weather kills more birds than all other sources of mortality combined. When unseasonably cold temperatures last more than three or four days, the birds starve for lack of insects. In the West, logging practices that remove dead trees can reduce nesting habitat for martins. Reduction of pesticide use on South American wintering grounds and protection of large winter roosts in Brazil is also important to the conservation of this species.Back to top

Backyard Tips

You can put out crushed eggshells to give the martins a source of grit for digesting insect exoskeletons.

Put up a Purple Martin house in your backyard, and you just might be treated to a close-up look at these engaging birds all through the breeding season. Attach a guard to keep predators from raiding eggs and young. Find out more about nest boxes on All About Birdhouses, where you'll find plans for building a Purple Martin nest box.

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Credits

Brown, Charles R. and Scott Tarof. 2013. Purple Martin (Progne subis), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski, Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley guide to birds, second edition. Alfred A. Knopf, New York, USA.

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