The Purple Martin (Progne subis) is the largest North American swallow of the family Hirundinidae. They are most prevalent in the Eastern United States and Canada during the breeding season, but they also have smaller populations in the Southwest and along the Pacific Coast. Their winter range extends throughout South America, including Brazil, Bolivia and parts of Peru.
Purple martins and other members of its genus are larger than most other swallows. The average length from bill to tail is 20 cm (7.9 in). Adults have a slightly forked tail. Adult males are entirely black with a glossy blue sheen, the only swallow in North America with such coloration. Adult females are dark on top with some steel blue sheen, and lighter underparts. Subadult females look similar to adult females minus the steel blue sheen and browner on the back. Subadult males look very much like females, but solid black feathers emerge on their chest in a random blotchy pattern as they molt to their adult plumage. The species was first described by Swedish zoologist Carl Linnaeus in his Systema Naturae in 1758 as Hirundo subis.
Purple martins are aerial insectivores, meaning that they catch insects from the air. The birds are agile hunters and eat a variety of winged insects. They will sometimes come to the ground to eat insects. They usually fly relatively high, so mosquitoes do not form a large part of their diet, contrary to popular opinion. Recent research does indicate that the purple martin feeds on invasive fire ants (Solenopsis invicta) and that they may make up a significant portion of their diet.
Martins make their nests in cavities, either natural or artificial. In many places, humans put up hollow gourds or houses for martins, especially in the east, where purple martins are almost entirely dependent on such structures. As a result, this subspecies typically breeds in colonies located in proximity to people, even within cities and towns. This makes their distribution patchy, as they are usually absent from areas where no nest sites are provided. Western birds often make use of natural cavities such as old woodpecker holes in trees or saguaro cacti.