Tree Swallows in the Mystic River Watershed  

Well folks, it is almost that time of year again—spring migration—when all the wintering birds return to breed and nest.  Tree swallows are due to arrive in late March and will be the first swallows to arrive this spring. 

Tree swallows are tiny little guys, just five inches long, weighing just under one ounce.  They sport a sleek metallic blue head and wings, and fuzzy white bellies.  A strip of black feathers resting over their eyes gives the appearance of a mask. 

Tree swallows thrive in open fields near forests and wetland habitat by rivers, lakes and flooded meadows. You may see them dart across the surface of the Mystic River or the Mystic Lakes, snatching bugs out of the sky.  As cavity nesters, they pad holes in trees or birdhouses with soft feathers and other materials.  Females will lay four to six eggs and wait patiently for the little ones to hatch in two weeks.  They will remain under both parent’s care until they leave the nest at three weeks old. During peak nesting times, parents may make 10-20 feeding trips per hour, collecting as many as 6-7000 insects a day! 

So why are we building birdhouses for the tree swallows?  

Although their populations across North America are relatively stable, the number of local tree swallows is limited by the number of available nest sites.  Over the last two centuries, natural cavity nest sites have decreased as forested wetlands were developed.  Bird boxes help to maintain their range. 

Interested in installing boxes with us? Each event is limited to 12 volunteers. If you sign up after all spaces have been filled, you will be placed on a waiting list. Sign up here.

Author: Zoe Davis, MyRWA TerraCorps Member