Tree Swallow

The Tree Swallow is a common aerial insectivore across North America, easily recognized by its glossy blue-green back and bright white underside. It is one of the earliest swallows to return in spring and readily nests in artificial nest boxes near water.

Because it nests in cavities and often in colonies around lakes, ponds, and marshes, molted feathers can sometimes be found near nest boxes or roosting sites, especially after the breeding season.

Its sharply contrasting two-tone feather coloration makes it one of the more distinctive swallow species to identify from a single feather.

Identifying Tree Swallow feathers

• Upperpart feathers: Iridescent blue-green to teal-green, shifting to more blue or greenish depending on the angle of light — a classic structural iridescence rather than pigment alone.
• Underpart feathers: Clean white with no streaking or barring, contrasting sharply with the dark upperparts.
• Flight feathers: Long, pointed, and dark blackish-green, built for fast, agile flight; primaries are notably long relative to body size.
• Shaft color: Dark on upperpart feathers, pale on white underpart feathers.
• Compared to similar species: Violet-green Swallow feathers show more green-violet iridescence and white extending onto the face and rump sides; Tree Swallow lacks white on the face or rump.

Plumage overview

Adults show glossy blue-green upperparts and immaculate white underparts, with a slightly notched tail. Females can appear slightly duller or browner than males, especially in their first breeding season, and some yearling females retain brownish upperpart feathers rather than full iridescence.

Juveniles are gray-brown above rather than iridescent, with a faint gray wash across the breast. A single annual molt occurs after breeding, mostly on the wintering grounds.

Habitat and range

Tree Swallows breed across most of Canada and the northern two-thirds of the United States, favoring open country near water — marshes, lakes, ponds, and fields — where flying insects are abundant and cavities (natural or nest boxes) are available.

They are strongly migratory, wintering along the Gulf Coast, Florida, Mexico, and Central America, and are notable for forming large, dense pre-migratory flocks that roost in marshland reeds.

Behavior and field notes

Tree Swallows feed on flying insects captured on the wing, and in cooler weather can shift to eating berries, particularly bayberries, which allows them to winter farther north than most swallows. They nest in cavities lined with grass and often distinctively lined with white feathers from other bird species.

Their call is a liquid, cheerful chirping and gurgling series. A key field note: if you find a small white feather stuck haphazardly at a nest box entrance, it may have been intentionally added as lining, since Tree Swallows famously collect feathers to line their nests.