North America’s largest swallow, the purple martin’s (Progne subis) nesting habits are influenced by the region it inhabits, with nest boxes preferred by populations in the eastern U.S., and natural crevices and hollows favored by birds resident in the west.
Our guide discusses the typical breeding behaviors and nesting habits of purple martins, so please read on to find out more.
Purple martins are cavity nesters, opting for nest boxes and gourds, cracks and crevices in buildings, or natural hollows in cacti and dead tree trunks. A nest of twigs and pine needles, lined with fresh leaves, is built inside the cavity.
Purple martins are communal nesters, and prefer to set up home in close proximity to neighboring birds of the same species. When nest boxes are set up, it’s a good idea to offer a number of different cavities to attract several pairs of nesting birds.
To learn more about the most suitable sites, designs, colors and sizes of boxes to use to stand the best chance of attracting nesting pairs of these large swallows, keep reading as our guide to purple martin nesting covers these topics in depth.
Male (left) and female (right) Purple Martins outside of their nest box
Purple martins breed across the southeast of the United States, with populations also breeding along the Pacific coast. Nests are constructed in cavities in trees, purpose-built houses, and inside cracks in buildings.
Geographical location influences the choices of nest site, with artificial nest boxes widely favored in the east, and natural sites utilized in the west.
Purple martins commonly revisit and reuse previous nest sites in subsequent years. If the previous nest structure remains in place, they will simply add new fresh green leaves as a nest lining.
Backyards are a common choice for nesting purple martins, particularly those where householders have carefully prepared for their arrival, by setting up specially designed houses for their summer visitors to raise their young in.
A wide range of style and designs of nest boxes and gourds are commercially available, with some rather elaborate layouts used in an attempt to provide luxury living quarters for these large visiting swallows where they can be observed at close range.
Purple Martin feeding one of their chicks outside of the nest box
Particularly in the eastern United States, purple martins are almost exclusively reliant on artificial nest boxes or gourd structures that are purpose-built to house the species. Manmade nest boxes are also used in the west, where nesting purple martins will also make use of natural hollows in trees and cactuses, and cracks and crevices in building walls and roofs.
Hollows in aspen and pine trees are commonly used by nesting purple martins in the west of the U.S. Other trees that may provide a suitable cavity excavated and since abandoned by another bird, include oaks, pines, spruces, Sabal palms and cypresses.
Saguaro cactuses are another popular site for a purple martin to nest in, with cavities high up in the stem offering a safe space in which eggs can be laid.
A colony of Purple Martins at a man-made bird house at the Parker River National Wildlife Refuge, Plum Island
There is no specific guidance about which direction a purple martin house should face – it’s more of an issue to ensure the house is positioned away from trees, so there are no obstacles to navigate when entering or exiting the cavity.
Common bird house designs feature numerous chambers and entrances, all facing in different directions, and more often than not, all will attract nesting purple martins, indicating there is no preference over the direction the opening faces.
The tradition of using hollowed-out gourds as nest sites for purple martins began with the Native Americans hundreds of years ago. Modern gourd-style nests follow the same basic principle, offering a simple nesting chamber.
Purple martin houses are available in a range of designs, with more elaborate structures featuring different compartments, entrances, and porch-style ledges.
Both styles will be welcomed by nest-seeking purple martins, which are not a particularly picky species when it comes to selecting a nest site. The location of the nest box is more of a priority than its appearance or internal layout.
Red Barn style Purple Martin house used by a colony of Purple Martins
Experts advise that the exterior of a house designed to attract nesting purple martins should be white. This is because white reflects the heat, meaning that internal temperatures inside the cavity are kept as cool as possible.
The optimum height for a purple martin house is between 3 and 6 m (10 to 20 ft) above ground level, with houses mounted on poles that are firmly staked in the ground.
After the breeding season has finished and purple martins have begun their migration to wintering grounds in South America, it’s recommended to thoroughly clean any detritus or old nesting materials from the nest boxes or gourds and perform some maintenance checks before they are used again in the next breeding season.
Male Purple Martin perched outside of nest
Nests constructed by purple martins inside their chosen cavity are flattish structures, consisting of three levels with different materials used for each level.
A platform of twigs and mud forms the base, and may also include small pebbles and snail shells. On top of this, a layer of interwoven twigs, pine needles, and grasses is crafted. The final touches are fresh green leaves, added as a nest lining, on which the eggs are laid.
As purple martins are opportunistic nesters, they will make use of any empty cavity they encounter, so there is enormous range between the size of nest chambers. The nest structure constructed at the base of the cavity measures around 9 to 10 cm (3.5 to 4 in) across.
The inside of a Purple Martins nest, with one day old chicks
Purple martins arrive on their breeding grounds in spring, and begin to establish nesting territories from March onwards. April is the ideal time of year for breeding to begin, with insects more widely available once winter conditions ease and warmer weather returns.
Incubation, by the female purple martin alone, lasts 15 to 16 days. Hatching takes place over the course of two to three days, and hatchlings grow quickly until they are ready to fledge at around 4 weeks of age.
Purple martins typically arrive in the U.S. from their wintering grounds in South America from March onwards at the earliest. Eggs are usually laid in April and May, although early laying has occasionally been recorded in late March.
Purple Martins usually start breeding in April
Purple martins construct nests in the base of the cavity they have selected, using materials including twigs and mud to form a roughly round platform base. On top of this, a flattened cup is constructed, using finer twigs, soft grasses and pine needles.
The female works to shape the nest, molding it into a solid, more sturdy structure using wet mud, and pressing her body against the inside to form a depression in which the eggs will be laid.
The final touches are soft green leaves, usually added by the male, to complete the nest before laying begins.
Male and female purple martins work together to construct their nest, although the bulk of the work falls to the female. Males supply some of the final materials, but chiefly act as an observer rather than actively helping with the building.
Nest crafting is a complicated art form, and can take three to four weeks to complete.
Purple Martin bringing materials back to construct the nest
Purple martin eggs are pure white and around 2.5 cm (1 in) in length. They are glossy and smooth and have no markings.
The average number of eggs per clutch is 4 to 6, although it is not unheard of for purple martins to lay between 2 and 8 eggs in each brood. A new egg is added each day until the clutch is complete.
Male purple martins may spend short periods sitting on eggs, but the absence of a brood patch in males means that they are not able to incubate the eggs – a duty that falls to the female.
Four Purple Martin eggs inside the nest
Around 26 to 32 days after hatching, purple martin chicks are ready to fledge. After leaving the nest, the young birds continue to be cared for by both parents for up to a month.
Purple martins raise one brood of chicks per breeding season. If an early nesting attempt fails, a second attempt may follow. Some reports of successful second broods do exist, but these are rare and not verified.
Purple Martin feeding a chick with a dragonfly
If their nest is raided or if a clutch fails to hatch, then depending on how early in the breeding season it is, purple martins may abandon their nest site. Attempts at a second brood may follow, with pairs likely to seek a new site in which to try again.
Ground nesting is highly unusual for purple martins, and they are far more likely to establish a nest in an artificial container or natural hollow than simply on the ground, due to the likelihood of being targeted by predators. Only one isolated report of ground nesting of purple martins exists.
In certain parts of the U.S., it is not unheard of for male purple martins to sleep in a different compartment of a nest box or gourd to where a female is raising young. More common, however, is the gathering of both male and female birds at dusk to congregate overnight in large roosts near water.
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