Like Purple Martins, Tree Swallows are cavity-nesting birds. They use holes made by other birds in dead trees. With so many dead trees being removed these days, Tree Swallows are now dependent on man-made nest boxes. They prefer locations near water.

Adult Tree Swallows are iridescent blue-green above with white below and a slightly forked tail.

Tree Swallows are the hardiest swallow species, returning early in spring and leaving late in fall. They winter in the southern U.S. 

Tree Swallows are highly social outside of the breeding season and form large flocks, especially during migration. Grass Island in the Connecticut River is a migration roost site with August-September populations of hundreds of thousands of swallows.

Tree Swallows are highly social outside of the breeding season and form large flocks, especially during migration. Grass Island in the Connecticut River is a migration roost site with August-September populations of hundreds of thousands of swallows.

Tree Swallows are highly social outside of the breeding season and form large flocks, especially during migration. Grass Island in the Connecticut River is a migration roost site with August-September populations of hundreds of thousands of swallows.

Tree Swallow nests consist of layers of grasses and thin twigs lined with feathers, usually white, from other species.

Tree Swallows are primarily insectivorous, however, they will supplement their diet with small quantities of fruit. This allows them to return north earlier in the spring than other swallows.

The Tree Swallow is listed as Climate Threatened in Audubon ‘s Climate Report.