Tree Swallow (Tachycineta bicolor)
by Joni James

Tree Swallow pair: courtship

Every mid- March, I anxiously await the return of my “friends” — Tree Swallows (Tachycineta bicolor). This year they returned to my home in south-central Indiana on March 12th. They had been gone since late July to August (last year) and had wintered south–perhaps as far south as Panama. Tree Swallows return a month before they begin nesting. I stepped outside and heard their bubbling song and a male landed above me on the utility line. I always become a little emotional upon their return for they are my constant companions during their time here. I have provided nesting sites for Tree Swallows and collected data for NestWatch (citizen science project www.nestwatch.org) for many years. I speculate the ones who have nested here previously are the swallows who perch close to me upon their arrival when I am in the yard.

Tree Swallows are a delight to observe. Head to marshes and open fields near bodies of freshwater to observe these graceful aerialists. They feed primarily on insects caught while in flight and will eat berries during cold spells when insects are not abundant. Tree Swallows are a about six inches in length with iridescent blue-green upperparts, white underparts and a notched tail. Females are duller and juveniles browner. You will often see them in large groups (often with other swallow species) perched on utility lines or flying over bodies of water.

Tree Swallows are cavity nesters. They will nest in natural cavities of dead trees as well as boxes and plastic gourds (which they seem to prefer at my home). Watching their courtship is entertaining as well as educational. Nesting begins when the female takes a strand of grass into the nest cavity showing her interest. There are numerous visual displays near the nest site. The two most common are “Flutter-flight” done by the male near the female and “Bowing” done together. If you are lucky, you may see the “Billing” display when the pair touch bills. Mating occurs approximately a week before egg-laying begins.

Nest building can take a few weeks to complete depending on the weather. The female does most of the building although the male will provide materials to her. The nest is made of grasses and lined with numerous feathers creating a lovely nest.

The female lays 5-6 pure white eggs and incubation takes about 11-20 days. The male will guard the nest when the female leaves. The female broods the young the first few days and both parents feed the nestlings. Nestling phase lasts 15—25 days. The fledglings are strong fliers upon leaving the nest,  although the parents will continue to feed them for several days before they are completely independent.

Get to know the Tree Swallow. Watch their acrobatics over fields and water. Put up boxes in the proper habitat and spend time observing the fascinating courtship and nesting behaviors of these swallows.  

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