The Tree Swallow (Tachycineta bicolor) is a familiar bird in our region, inhabiting open areas, usually near water, in the nesting season. Like our other swallows, it is an aerial insectivore, catching its prey almost exclusively on the wing, during the course of a graceful, smooth, languid flight pattern typically consisting of long glides punctuated by a short series of quick flaps. This bird gets its name from its choice of nest site, cavities in trees, although it will also readily accept birdhouses.
In good light, the Tree Swallow is a stunningly beautiful bird with clean, pure white underparts making a striking contrast with its upperparts which are an iridescent electric blue, often showing green highlights, depending on the angle of the light illuminating the bird. Its usual vocalization is a pleasant, liquid twitter given especially frequently around the nest site.
This is the first swallow to come back in spring, and the last to leave in fall. The first few birds of this species show up in early to mid-March, and Tree Swallows are present in our area sometimes even into December (generally on the coast). This remarkable range of dates is due to this species’ ability to subsist on vegetable matter, mainly bayberries, when temperatures are too low to allow the presence of flying insects.
In fall migration, their night roosts can number in the hundreds of thousands, and a large foraging flock at this time of year swooping down to feed in bayberry bushes can also be a spectacular sight, as the birds often form a long, swirling, tornado-like column of birds as they descend.
The Tree Swallow is considered Climate Threatened with a 56 percent loss of current winter range and a 61 percent loss of summer range. As its range drifts north, nesting sites such as dead trees or boxes will become increasingly important.