Biology (according to Nature Canada)
The Purple Martin (Progne subis) is the largest species of swallow in North America. Purple Martins breed throughout North America and make an incredible migration to the Amazon basin of Brazil for the winter.
The Purple Martin eats insects. The Purple Martin is part of a group of species called aerial insectivores that feed on flying insects. Other examples include swifts, swallows, fly-catchers, night-jars, and whip-poor-wills. Purple Martins mostly eat larger prey like dragonflies, moths, mayflies, and even butterflies!
Purple Martins are declining: Aerial insectivores (including the Purple Martin) are in serious trouble. They are experiencing widespread population declines, yet the exact cause remains unclear. Many possible culprits have been suggested including environmental threats along their migratory route and at their wintering grounds (deforestation in the Amazon), decrease in food availability, inability to adapt to climate change, nest site competition with invasive species (particularly Starlings and House Sparrows), exposure to pesticides, and industrial development projects.
Purple Martins love humans! West of the Rocky Mountains, Purple Martins nest mainly in natural cavities such as old woodpecker holes. However in the east, they nest almost exclusively in apartment-like nest houses provided by their human ‘landlords’ this tradition of human dependence have been in place for centuries. Purple Martin landlords take care of their birds by maintaining their house and monitoring the nests. They also help provide protection against predators such as squirrels and hawks, and keep martins safe from aggressive intruders such as Starlings and House Sparrows.
There are three subspecies of Purple Martin. The eastern subspecies s. subis is the most widespread and nest in colonies in human-constructed bird houses throughout eastern and mid-western North America. The western subspecies, P. s. arboricola can be found west of the Rocky Mountains in California and British Columbia. They are known for nesting in natural cavities such as abandoned woodpecker holes, but are increasingly making use of nest boxes as a result of a program that began in the 1980’s to recover local populations of the species. The desert southwest of Arizona and Northern Mexico hosts a lesser known subspecies, P. s. Hesperia, that breeds in natural cavities in saguaro cacti and do not tend to form dense colonies.
PURPLE MARTIN FACTS
- Average size: 7.5 inches long, 15-16 inch wingspan and weigh about 2 ounces.
- Color: Adult males have dark plumage (black, blue, purple), with dark purple feathers on their head, throat and belly. Adult females are lighter in color, more gray brown and white, but also have purple feathers on their head and back.
- Habitat: East of the Rockies, purple martins nest almost entirely in homes provided by people, such as bird houses. Native Americans, particularly Choctaw and Chickasaw, have made homes for the birds for centuries.
- Diet: Martins are primarily aerial insectivores, which means they eat insects while flying. Contrary to popular belief, martin’s don’t eat many mosquitoes, since they feed higher in the sky and during the day.
- Nest: Built of pine straw, twigs and mud and lined with green leaves.
- Eggs: Martins average about 4 to 6 eggs per clutch, which incubate for about 16 days.
- Migration: Thousands of purple martins migrate annually from Canada to Brazil—a trip which takes about 4 to 6 weeks and covers 5,000-6000 miles each way.