The mature tree swallow has a distinctive iridescent sheen on its blue-green back (this is brown in immature birds) and the underside is bright white from the throat to the beginning of the tail. Tree swallows are found in open places near water such as marshes, lake shores and flooded meadows. They mostly eat insects caught in flight, but will also feed at ground level on spiders, small crustaceans, berries and seeds. These swallows nest in tree cavities, often using old woodpecker holes. Other nesting sites include nesting boxes and mail boxes.

The tree swallow is unusual in that the immature plumage lasts through the first year or longer. This means that immature birds can be around nesting sites of breeding birds without being in a competitive situation.

Bluebird nesting boxes that were erected on the periphery of the wetland area have been used by tree swallows for several years. Another nesting box was used by a mouse.