Badger Tracks

By Anita Carpenter

The Gentle Tree Swallow

     Spring's warmth is in the air. The sky is a clear, beautiful blue. Tree buds are swelling. Overhead, soft, cheerful twittering notes are welcome music to my ears. I look up and rejoice for the first Tree Swallows of the year have returned. On pointed wings, the slender, graceful aerialists are plying the skies looking for elusive insects.

Tree Swallows, Tachyineta bicolor, are the first of the six species of swallows found in Wisconsin to repopulate the state. They arrive in late March to early April. Many nature lovers consider them a harbinger of spring.

     Tree Swallows are easy to identify. Sexes look alike. The 5-1/2-inch birds have glistening, blue-black backs and pure white underparts. Sun and light play with the intensity and shade of the blue color.

     These beautiful, friendly birds are secondary cavity nesters. That is, they depend on pre-existing cavities, such as an old woodpecker hole or a nest box provided by a caring individual. As bluebird enthusiasts know, Tree Swallows often usurp a bluebird box for their own use. The pair is protective of their chosen box and will aggressively dive bomb you if you come too close.

     Upon their return in spring, Tree Swallows are not in any hurry to initiate nesting, which begins in late April to early May. Then the female becomes a very busy bird. She builds the nest, which may take 2 to 4 weeks to complete using dried grasses that she picks up from the ground. She often incorporates white feathers into the nest. She lays 4 to 7 pure white eggs, one per day, and then incubates them for 14 to 16 days. Often the male is patiently perched nearby. 

     Once the eggs hatch, both parents diligently participate in feeding the youngsters a diet of insects. Interestingly, the adults pack the captured insects into a B-B-sized ball, called a bolus, and feed it to a nestling. It takes many, many insect-catching forays to feed the hungry family. The young fledge in 18 to 22 days. One brood is raised per year. The total nesting period lasts 45 days.

     As beautiful as Tree Swallows are, they are not fastidious housekeepers. Look inside a nest box after the swallows have left. I would not want to grow up in such a mess.

     Soon it's time to prepare for migration. Tree Swallows are one of the earliest birds to leave their breeding areas. They quietly begin to disappear in July and gather in large flocks. They are often seen in big numbers perched on wires, on tops of stems or cattails, or on roofs. They will begin their journey south to the Gulf Coast in August. They tend to winter farther north than all the other swallows that nest in Wisconsin.

     Tree Swallows are insect eaters. They feed while flying with their mouths wide open to scoop up the flying insects. They are fast flyers that make quick, sharp turns in pursuit. They may fly close to the ground or high in the sky, depending where the insects are, which is often dependent on weather conditions.

     These agile birds not only eat on the wing, but they also drink and bathe on the wing. While in flight, their beaks gently touch the water surface repeatedly to drink. To bathe, they deliberately touch and splash the water several times with the spray striking the feathers.

     I never tire of watching Tree Swallows and their amazing abilities of flight. To more closely enjoy these gentle birds, why not put up a Tree Swallow nest box. Just don't be surprised if a Black-capped Chickadee or House Wren competes for the same nesting site. Whoever is successful in claiming the box, enjoy the avian entertainment.