Purple martins are members of the swallow family, the largest swallow in North America. This species of bird migrates from the United States for the winter and then comes back each spring to breed and raise its young.
The purple martin depends almost entirely on flying insects for its food source, meaning that when cold weather approaches and these insects cease all activity, the martin must fly to warmer climates.
The breeding range and summer home of this bird includes most of the eastern U.S., parts of the Pacific Coast and Mountain States and some of Southern Central Canada. The martin will overwinter in South America, as far south as southern sections of Brazil.
The martins congregate in huge flocks that may be as large as hundreds of thousands of birds as they prepare to head to South America for the winter. This occurs in the fall, according to the New York Wild.org website. Most of the martins leave the U.S. by October for southern borders.
The purple martin returns to the southern portions of its range long before it comes back to the most northerly places it breeds. For example, martins start to show up in Florida in the middle of January, but those that breed in New England may not appear before May.
The Whatbird.com website states that almost all of the purple martins of the eastern U.S. nest in birdhouses provided for them by people.