Tree Swallows fly with intense intent as they forage over water for insects. This bird was photographed in April, when its early return made serious work of finding insects for food. Tree Swallows capture all of their food on the wing. They can share nesting territory with Eastern Bluebirds because the latter feed on insects found on the ground. They don't compete for food, but will compete for nesting cavities, both species using cavities exclusively. You often see what are commonly known as bluebird houses (nesting boxes) set out in pairs. Swallows will take one, then defend the territory from use by other Tree Swallows. This leaves the second box open for use by bluebirds.