Tree Swallow

Bird of the Day, March 25, 2020

Tree Swallow
Tachycineta bicolor

Originally published September 16, 2015

by Andy Griswold

What a Tree Swallow looks like: This common bird species with its handsome deep-blue back and crisp white belly and throat should be familiar to anyone who gets outside between March and October. You may even have a pair nesting in one of your yard’s bluebird boxes. Tree Swallows are a hole-nesting species, using old woodpecker nesting and feeding holes across the northern two-thirds of North America. It is among the best studied species in North America.

Measuring just under six inches and weighing about three-fourths of an ounce (about the weight of three quarters), these streamlined, broad-winged aerialists are relatively easy to separate from other east coast swallow species. Males are distinctive, with their iridescent blue-green backs. Females are more brown across the back and juveniles uniform gray-brown.

Juveniles from May through September will show a pale grayish breastband similar to Bank Swallow. Some adult females may have a weak breast band, too. In all plumages, Tree Swallows have a slightly notched tail, unlike the longer, deeply forked tail of the Barn Swallow and the square tail of the Northern Rough-winged Swallow.

Where and how to find it: Throughout the spring and summer Tree Swallows are easily found in fields, marshlands, along the coast, usually associated with some body of water. A good place to find them is in beaver ponds where there is always a proliferation of woodpecker holes and good feeding habitat. Tree Swallows have a high-insect diet but can also feed on fruits such as bayberry.

As for the fall spectacular on the Connecticut River, longtime Old Lyme resident Roger Tory Peterson wrote, “I have seen a million flamingos on the lakes of East Africa and as many seabirds on the cliffs of the Alaska Pribilofs, but for sheer drama, the tornadoes of Tree Swallows eclipsed any other avian spectacle I have ever seen.”

Often seen with Tree Swallows in their habitat of field and marshland are Barn Swallow and Purple Martin. On the roost site, expect to see the occasional Peregrine Falcon or Merlin making a pass through the flock.

Conservation status: Tree Swallows are common but have seen a steady decline observed in breeding bird surveys since 1966, measuring a cumulative decline of over 36 percent. Despite this significant loss, the species is not listed as a species of concern.

One can help by offering bluebird boxes as nest sites, since many natural sites have disappeared, with lands being developed and standing deadwood removed. Managing lands for this species is needed, making it important to encourage open field habitat and not discourage beaver activity. Pesticide exposure is also a concern for this insectivorous species.

Photo by Mark Jankura.