The purple martin (Progne subis) is a swallow native to North America. It is the largest type of swallow on the continent and is unique in that it is almost entirely dependent upon man-made nesting structures in many parts of its range. Nonnative birds introduced to North America such as the common starling have led to a decline in populations in the eastern U.S. and conservation associations are working to help this beneficial bird.
At about eight inches in length, purple martins are larger than other swallows. They are easily recognizable by their steely black color with a blue sheen and slightly forked tail. Purple martins can be found throughout temperate North America in the summer and migrate to South America each winter.
Purple martins have long had a relationship with humans as they help reduce insect populations. Long before European settlement, Native Americans would hang or erect hollowed out gourds as martin houses as the birds prefer to nest in cavities. Though purple martins in the west may still nest in natural cavities in trees, rocks or abandoned woodpecker nests, birds farther to the east are now completely dependent upon man-made structures and have thus expanded with human populations.
Purple martins are aerial insectivores, meaning that they feed exclusively by catching flying insects in mid-air. Contrary to popular belief, purple martins do not prey upon mosquitoes as the birds fly too high when hunting. Because of their hunting habits, martins prefer to have their nesting cavity or colony surrounded by at least 60 feet of open ground in all directions. Many bird lovers lose their martin colonies when trees begin to mature and encroach on the birdhouse.
Purple martin houses can contain many compartments and in some cases house over a dozen nesting pairs and their young; they require vigilant care by the human owner to keep the martins there and make sure they come back next spring. Nonnative starlings and robins can and will evict and kill purple martins; it is recommended that specific housing guidelines and care instructions be followed by anyone who elects to erect an artificial martin house. If a nesting site is well-maintained and free of predators, purple martins will return to it each spring for the rest of their lives.
Purple Martin Facts
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The first purple martins to arrive at a nesting site each spring are called “scouts”. It was once thought that these early arrivals were scouting out the nesting site to make sure it was still appropriate for the rest of the colony, but it is now known that these scouts are simply older martins returning to a site at which they have nested before.
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Purple martins drink in flight by flying low above lakes and ponds and skimming water with their lower beaks.
References
The Purple Martin Conservation Association
http://purplemartin.org/main/mgt.html
The Cornell Lab of Orinthology
http://www.allaboutbirds.org/guide/Purple_Martin/lifehistory
