Juveniles are a dull gray brown. The tail and wings are slate brown with a slight greenish tint. The belly and breast are white, and often the breast has a faint gray band. In winter, they migrate to Mexico, Florida, and Central America, but they occasionally winter as far north as the mid-Atlantic coast and the central valley of California. Tree Swallows prefer open habitats, such as the edges of woods, and areas near water, including marshes, shorelines, and swamps.
Tree Swallows are quite tolerant of humans.
They forage over land and water, swerving and dipping to feed on flying insects such as beetles, midges, crane flies, horseflies, ants, moths, grasshoppers, dragonflies, and mayflies. In winter, they sometimes feed on berries, especially those of the wax myrtle. Tree Swallows and Myrtle Warblers are the only birds that can digest these berries, and this might help explain why Tree Swallows winter farther north than any other North American swallow. Tree Swallows forage mainly near their nest sites, either alone or in loose flocks. They are solitary nesters, but they may nest in loose aggregations with nests 10 to 15 meters from one another.