The purple martin belongs to the hirundinidae family and is usually about 7.5 inches long at maturity. The purple martin is the largest of the swallows. Its feathers are a dark blue-black with the females' underside being a bit lighter. The purple martin catches its food by flying through the air in circles, scooping up insects as it flies along. It breeds in the United States and winters as far south as southeast Brazil. Purple martins make their nests in tree holes that are lined with mud and sticks. Some people, hoping to attract purple martins, make birdhouses on tall poles and place them in their backyard.
The tree swallow is smaller than the purple martin, averaging about 4.5 inches long. It has a white underside, while its top portion is a dark, shiny blue-green. The tree swallow lives in thinly wooded areas that are usually near water, where it can catch insects. Tree swallows will make their nests either inside a birdhouse or in the cavity of a tree or building. It's not uncommon for large flocks of tree swallows to gather together when migrating. The tree swallow breeds throughout North America but can migrate in winter as far south as Colombia.
Barn swallows are about 6 to 7 inches long. They have a deeply forked tail, like all swallows, with a chestnut-colored throat; their underside is a buff color and their upper portion is blue-black. Their nests are usually made of mud and are located in the rafters of barns, walls, roofs, bridges or caves. These swallows breed in North America and spend their winters in the Southern Hemisphere.
The bank swallow is small, between 4 and 5 inches in length. Its underside is white, and its upper portion is brown; it's quite drab in color compared with some of the other swallows. The bank swallow has powerful, slender wings, well suited for long-distance flight. As its name suggests, it lives by steep river banks and sand pits, hunting for insects by the river. The bank swallow uses plant material to construct its nest, in a tunnel made in a bank or cliff.