Tree Swallow (Tachycineta bicolor)
The Tree Swallow is a common sight in central Alberta. This distinctive blue and white Swallow gracefully chases insects above rural agricultural fields. They spend almost all of their time flying and catching insects. Despite how common they are, they are in decline.
HOW TO IDENTIFY
To identify the Tree Swallow, look for these distinguishing features:
- Vivid blue back, head, and wings, though these may appear grey in young birds.
- White underside.
- Very small and flat bill.
- Very long wings compared to the rest of their bodies.
- Small size: Tree Swallows are 12-15 cm in length, up to a whopping 25g in weight, and a wingspan of 30-35 cm.
Identify in Flight
To identify the Tree Swallow as it flies by, look for these clues:
- Extreme grace and agility while flying. Will dive and perform other acrobatic maneuvers to catch insects.
- Long wings.
- White underside and vivid blue upperparts.
Identify by Sound
Tree Swallows have a chattering song that they frequently make while flying and while stationary. Because they often gather in large numbers, they can make quite the racket!
WHERE TO FIND
You can find Tree Swallows in all parts of North America except the high Arctic. They breed from the tundra to the central United States, and they winter throughout most of Central America.
Despite their name, Tree Swallows prefer open areas like agricultural fields or wetlands. They get their name from their tendency to nest in tree cavities. This protects their young from predation. They like to be near wet or open areas because wetlands produce much of their preferred food.
Tree Swallows breed in fields, marshes, shorelines, wooded swamps, and beaver ponds throughout northern North America, preferring to live near bodies of water that produce multitudes of flying insects for food. For nesting they need old trees with existing cavities (typically made by a woodpecker), or human-made nest boxes. Migrating and wintering birds use habitats similar to their breeding habitat, except they may have no need for cavities and are free to live in open areas.
SOCIAL LIFE
Tree Swallows are highly social, forming large migratory and wintering flocks; and pairs often nest close together, particularly where nest boxes are numerous. Agile fliers, Tree Swallows tend to glide more than any other swallow species. They bathe by flying low over the water and skimming their bodies against the surface, then rising quickly while shaking off droplets. Tree Swallows line their nests with feathers, and they seem to display or even play with these feathers during the early nesting season. A bird flies above the nest with a feather held in its bill; sometimes this leads to chases, and sometimes the bird drops the feather, causing an aerial free-for-all to see which bird retrieves it.
Tree Swallows pair up to breed but often mate secretly outside the pair. Occasionally a male attends two mates in separate nest sites. Though an individual swallow may have the same mate several years in a row, it is probably faithful to the site rather than the mate. Nest predators include rat snakes, raccoons, black bears, chipmunks, mink, weasels, deer mice, feral cats, American Kestrels, Common Grackles, American Crows, and Northern Flickers. Outside the nest, adults are hunted by Sharp-shinned Hawks, Merlins, Peregrine Falcons, Great Horned Owls, and Black-billed Magpies. The swallows commonly swarm and dive-bomb predators while giving alarm calls.
They are very social and like to breed in large groups.
Sometimes they take the same mate year after year.
They are migratory. They breed in Canada, spend a couple of months resting up in the central USA, then fly to Central America for the winter.
NEST PLACEMENT
Tree Swallows nest in natural cavities of standing dead trees, old woodpecker cavities, or nest boxes. On occasion they nest in hollow stumps, building eaves, Wood Duck nest boxes, holes in the ground, old Cliff Swallow burrows, or other unconventional sites.
NEST DESCRIPTION
The female does most of the nest building, taking between a few days and two weeks to finish the job. She collects material on the ground near the water’s edge, usually within 100 feet of the nest site. The nest is often made entirely of grass, but may include pine needles, mosses, rootlets, aquatic plants, animal hair, and artificial materials like cellophane or cigarette filters. Within the cavity, the female presses her body against the nest material to shape it into a cup, about 2–3 inches across and 1–2 inches deep, and lines it with many feathers of other bird species. In some populations the male gathers most of the feathers, and in others the male and females split the duty evenly.
FOOD CHAIN
Tree Swallows live on a diet of insects, though they occasionally capture other small animals and may eat plant foods during bad weather when prey is scarce. They feed from dawn to dusk in sheltered areas full of flying insects, usually foraging no more than 40 feet from the ground. Tree Swallows eat all kinds of flying insects: dragonflies, damselflies, flies, mayflies, caddisflies, true bugs, sawflies, bees, ants, wasps, beetles, stoneflies, butterflies, and moths, as well as spiders, mollusks, and roundworms. Their prey may be smaller than a grain of sand or up to two inches long. They chase prey in the air, with acrobatic twists and turns, and sometimes converge in large numbers in an insect swarm. During the breeding season, Tree Swallows eat high-calcium items like fish bones, crayfish exoskeletons, clamshells, and eggshells of gulls or loons.
They primarily eat insects that they must catch by flying. This includes a wide variety of insects including: dragonflies, damselflies, flies, mayflies, ants, wasps, beetles, stoneflies, butterflies, and moths.
In the nest, their eggs and young may be predated by raccoons, black bears, chipmunks, mink, weasels, deer mice, feral cats, American Kestrels, Common Grackles, American Crows, and Northern Flickers.
Outside the nest, adult Tree Swallows can be predated on by other bird species, including: Sharp-shinned Hawks, Merlins, Peregrine Falcons, and Black-billed Magpies.
FUN FACTS
- Tree Swallows use nest boxes. As forests and dead trees are cut down, these birds lose habitat. You can put up a nest box to counter this.
- Tree Swallows are some of the most graceful birds in the air, relying on incredible acrobatics to catch insects while flying.
- Migrating and wintering Tree Swallows can form enormous flocks numbering in the hundreds of thousands. They gather about an hour before sunset and form a dense cloud above a roost site (such as a cattail marsh or grove of small trees), swirling around like a living tornado. With each pass, more birds drop down until they are all settled on the roost.
- Tree Swallows winter farther north than any other American swallows and return to their nesting grounds long before other swallows come back. They can eat plant foods as well as their normal insect prey, which helps them survive the cold snaps and wintry weather of early spring.
- The Tree Swallow—which is most often seen in open, treeless areas—gets its name from its habit of nesting in tree cavities. They also take readily to nest boxes.
- Tree Swallows have helped researchers make major advances in several branches of ecology, and they are among the best-studied bird species in North America. Still, we know little about their lives during migration and winter.
- The oldest Tree Swallow on record was at least 12 years, 1 month old when it was recaptured and released during banding operations in Ontario in 1998.
how you can help
Build Tree Swallow at Nest Box
Don’t use pesticides in your garden or farm, particularly neonicotinoid pesticides. These wash into natural waterways and reduce insect numbers so the Tree Swallows don’t have as much food to eat.
Put up a nest box. Tree Swallows like open areas such as agricultural fields.
Support protected areas in the Edmonton region (such as EALT!). You can donate or volunteer your time to help with conservation efforts.
Reduce your carbon footprint to reduce impacts of climate change.