Beautiful and Graceful, the Tree Swallows Have Returned

March 11, 2024

During the last two weeks, I have noticed high above me the sweet twitters and chirps of those excellent aerial flyers, the swallows. This week, I finally got a good look at a perching swallow resting in the rain atop some tule plants. Seeing these beautiful birds sitting instead of doing aerial acrobatics above my head or over the water is a treat. Tree Swallows (Tachycineta bicolor), are some of our earliest neotropical migrants, arriving from their winter homes from Northern Mexico to Panama. This swallow breeds in Mendocino County and as far north as Alaska. Tree Swallows often appear in large flocks perching on telephone wires.

The males are bright, iridescent blue-green with bold white underparts, including the belly and chin. The females and juvenile birds are duller, brownish-gray, and have no iridescence. They have a compact shape, fairly broad wings, and a slightly notched tail.

Tree Swallows live in a variety of open habitats, generally near water. They live in grasslands, marshes, and in proximity to lakes. They are called secondary cavity nesters because they do not excavate their own cavities. They must use abandoned cavities built by primary cavity excavators such as woodpeckers, Oak Titmice, and nuthatches or find another natural cavity in a tree. One factor that has increased the population of Tree Swallows is the popularity of building Western Bluebird houses, which has turned out to be a boon for the swallows as their nesting sites, such as dead trees, have decreased with urbanization and development. Swallows readily nest in Western Bluebird boxes. If you want Tree Swallows nesting near your home, visit the website Nestwatch.org. Check out their “all about birdhouses” for instructions on building or purchasing the best type of swallow nesting boxes, where to locate them, and how to prevent predators or invasive species from using them.

If you have problems with mosquitos or other biting insects, having a Tree Swallow nest is an excellent way to mediate this problem. An adult Tree Swallow can consume 2,000 flying insects per day. With a pair of Tree Swallows raising their young, this could add up to more than 5,000 flying insects. This tremendous natural insect control could bring you and your family hours of entertainment.