Tree Swallow

The Tree Swallow is a small, streamlined songbird known for its dazzling, metallic plumage and spectacular aerial maneuvers. Highly social and often tolerant of human activity, this species is a frequent occupant of backyard nest boxes across North America. Unlike most other swallows, Tree Swallows are capable of digesting wax-myrtle and bayberry fruit, allowing them to survive cold snaps and winter farther north than their relatives. They are extensively studied by scientists and serve as a model species for understanding avian ecology and environmental health.

Adult male Tree Swallows are unmistakable when seen in good light, presenting a starkly contrasting pattern of deep, iridescent blue-green upperparts and clean, unmarked white underparts. They possess a thin, black eye mask and a slightly notched tail.

• Adult Females: Can be similar to males, but younger females (one year old) are dull brown above with variable amounts of blue-green sheen.
• Juveniles: Are uniform grayish-brown above and white below, occasionally showing a faint, incomplete dusky wash or band across the breast.

Similar Species:

• Violet-green Swallow: Best distinguished from Tree Swallows by the white patches wrapping around the sides of the rump and extending up behind the eye.
• Barn Swallow: Differs by its deeply forked tail, rufous underparts, and dark throat.
• Bank Swallow: Distinctly smaller, with a well-defined dark band across a white breast.

During the breeding season, Tree Swallows occupy open and semi-open habitats, particularly those near flat water such as marshes, ponds, lakes, and wet meadows. They require standing dead trees (snags) with abandoned woodpecker holes or human-made nest boxes to breed.

Their breeding range spans the northern and central United States up through Canada and Alaska. In late summer and autumn, they migrate in massive flocks to their wintering grounds in the southern United States, Central America, and the Caribbean, where they frequent coastal lagoons, marshes, and agricultural fields.

Tree Swallows are master aerialists, catching flies, beetles, dragonflies, and other insects directly in mid-air with acrobatic swoops and glides. They fly with a mix of rapid flaps and graceful glides, often foraging low over water surfaces.

• Nesting: They are secondary cavity nesters, using natural tree cavities or nest boxes. The female constructs a cup nest lined with grass, pine needles, and feathers (often gathered while performing aerial swoops).
• Vocalizations: Their calls are cheaping, liquid chirps and twittering buzzes given in flight or while defending nesting sites.
• Social Structure: Outside of the breeding season, they form massive communal roosts numbering in the hundreds of thousands, creating swirling, cloud-like funnels in the sky at dusk before settling into reed beds.