Spring migration continues at a fever pitch with warblers, sparrows, and all kinds of other birds coming through. A member of the swallow family, the tree swallows are widely distributed nesting birds on Cape Cod. They typically breed close to water in open habitat such as fields, marshes, lakes, and swamps. Nests are established in natural cavities as well as man-made nest boxes. The tree swallow is known for its iridescent blush green upperparts and brilliant white underparts. This tree swallow was seen fluttering its wings atop a fence post near a nest box at Bourne Farm in North Falmouth.