Although they overwinter throughout much of South America, Purple Martins (Passeriformes: Hirundinidae: Progne subis) migrate long distances in the spring and nest throughout much of North America. Long before humans came onto the scene, these birds selected nests in tree cavities and in crevices in rocks and cliffs.
At some point Native Americans started hanging hollowed-out gourds for Purple Martins to nest in. After European settlers arrived in North America they adopted this practice, providing a variety of nest boxes. The tradition became widespread in the east throughout the last two centuries, and today eastern populations of Purple Martins nest almost exclusively in these human-made structures. Smaller western populations still nest the old-fashioned way, where artificial nest boxes never caught on.
Purple Martins feed on a wide variety of flying insects, capturing them in mid-air. They’re particularly common in areas that harbor large numbers of these insects, especially around lakes and ponds. Sudden cold periods can have a detrimental effect on these birds, since the weather grounds most of the insects that they rely upon for food. Bad weather, in fact, is the single biggest factor in Purple Martin mortality.