Tree swallow

Tachycineta bicolor

Last updated: June 4, 2021
Verified by: AZ Animals Staff
© Elliotte Rusty Harold/

The tree swallow can make more than a dozen distinct vocalizations


Tree swallow Scientific Classification

Scientific Name
Tachycineta bicolor

Read our Complete Guide to Classification of Animals.

Tree swallow Conservation Status

Tree swallow Locations

Tree swallow Locations

Tree swallow Facts

Insects, berries, and seeds
Fun Fact
The tree swallow can make more than a dozen distinct vocalizations
Estimated Population Size
20 million
Biggest Threat
Loss of nesting sites
Most Distinctive Feature
The iridescent greenish-blue plumage
Incubation Period
11-19 days
Meadows, marshes, and shorelines
Snakes, raccoons, weasels, cats, chipmunks, falcons, hawks, owls, and magpies
Common Name
Tree Swallow
Number Of Species
North America
Nesting Location
Hollows and holes
Age of Molting
15-25 days

Tree swallow Physical Characteristics

  • Blue
  • Black
  • White
Skin Type
Top Speed
30 mph
4.7-5.5 inches

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Easily identified by the iridescent hue of the plumage, the tree swallow is among the most common song birds of North America. Their complex sounds cut through the crisp spring air of the breeding season. The popularity of other song birds like the bluebird and house sparrow has benefited the tree swallow as well; all of them share an affinity for the same artificial nesting holes.

4 Amazing Tree Swallow Facts!

  • Tree swallows spend most of their lives flying in the air or resting on high perches. They try to spend as little time as possible on the ground, where they are most vulnerable to predators.
  • The tree swallow is an important cornerstone of the local food system wherever it’s found. It keeps a check on insect populations and also provides an excellent source of food for other predators.
  • Females produce their eggs in a staggered sequence of one per day until all of them have been laid. This allows the mother to prioritize older chicks in times of food scarcity.
  • The tree swallow is considered to be a model organism. Scientists study this species to learn new facts about other species.

Where to Find the Tree Swallow

The tree swallow has a truly massive range encompassing almost all of North America, from Alaska in the north to Panama in the south. They’re also sometimes found on the Caribbean islands. Tree swallows tend to live near meadows, marshes, shorelines, and wooded swamps.

Tree Swallow Nests

The tree swallow takes up residence in small tree hollows, standing dead trees, nest boxes, and even buildings or houses. Their nests are composed of grass, moss, weeds, roots, pine needles, and other plant matter. The nests are then lined with bird feathers (not their own) to provide comfort.

Tree Swallow Scientific Name

The scientific name of the tree swallow is Tachycineta bicolor. Tachycineta, which means “quick moving” in Greek, is a genus of American swallows. The name bicolor obviously refers to the pattern of the feathers.

Tree Swallow Size, Appearance, and Behavior

The tree swallow is a small bird, measuring up to 5.5 inches in length and weighing around 20 grams. It has small feet, a forked tail, and relatively large wings compared to body size. By far the most conspicuous feature is the iridescent green-blue feathers adorning the back and head. This is contrasted with the white breast and the black fringes on the wings and eyes.

One of the more unusual facts is that the tree swallow has two different social arrangements depending on the seasons. For most of the non-breeding months, it congregates together into huge flocks of thousands to roost at night. But this behavior suddenly changes in the breeding season, when the competition for nesting sites becomes incredibly fierce. Tree swallows will aggressively defend a territory about 30 to 50 feet around the nest from other members of the same species.

The tree swallow primarily communicates with each other through complex vocalizations. Up to 14 different calls have been identified that correspond with various emotional states and behaviors, including anxiety, physical attraction, submission, distress, and even a desire for food. These calls are generally composed of three parts (or a combination of these parts): a chirp, a whining sound, and a gurgle. While both sexes can make these standard calls, only the males are fully capable of singing. These songs appear to be a form of territorial signaling against potential interlopers.

Tree Swallow Gets its Target - a tree swallow grabs its target as it flies over the water surface of a pond. Silverthorne, Colorado.
Tree Swallow Gets its Target – a tree swallow grabs its target as it flies over the water surface of a pond. Silverthorne, Colorado.

©Richard Seeley/

Tree Swallow Migration and Timing

These birds migrate together in large flocks toward the southern United States and Mexico for the winter. This process begins as early as July and peaks sometime in the fall.

Tree Swallow Diet

These birds spend most of the day from dawn to dusk foraging for food; it sometimes travels several miles in search of good foraging opportunities. The bird’s main feeding strategies are to capture prey while in flight or skim along the surface of the water with its mouth open. Sometimes large groups of the birds can be seen gathering where insects are particularly abundant.

What does the tree swallow eat?

These birds are omnivores. The bulk of its diet consists of insects like flies, grasshoppers, beetles, and flying ants. The remaining 20% or so consists of plant materials like berries and seeds. This serves as a very good adaptive strategy. While purely carnivorous birds might starve during the winter, this species can survive on only plant material for long periods of time.

Tree Swallow Predators, Threats, and Conservation Status

These birds are considered to be a species of least concern by the IUCN Red List. There are currently no significant threats to this species besides natural predators. However, its survival is highly dependent on the availability of good nesting sites, which vary considerably from place to place. There is also some question on the long-term effects of pesticides on this species.

What eats the tree swallow?

An adult bird is preyed upon by larger birds such as magpies, falcons, owls, and kestrels. Juveniles and eggs are also vulnerable to raccoons, chipmunks, weasels, snakes, and cats. Groups of swallows will attempt to drive off a predator by mobbing it.

Tree Swallow Reproduction, Young, and Molting

These birds begin the annual breeding season in spring by forming temporary breeding pairs with a partner. Males will try to court females by showing them its potential nesting sites. While most birds remain monogamous, some will have multiple breeding partners each year.

Copulation usually takes place in the summer. After building its nest, the mother lays anywhere between two and eight eggs at a rate of one per day. These eggs take about 14 or 15 days to fully incubate. Both parents take part in feeding the juvenile chicks, but this helpless state does not last for very long. About 15 to 25 days after hatching, the juveniles are ready to leave the nest for the first time; they may still stick around for a short period while learning how to fly and receiving some food from the parents, but they must be fully independent by the time migration begins in late summer or fall. The chicks reach a state of full sexual maturity by the next breeding season.

Unfortunately, this high reproductive rate is a strategic necessity, because the survival rate of an adult tree swallow is quite low; only about 40 to 60% are estimated to survive each year. This makes their average life expectancy a mere 2.7 years. The oldest ever known tree swallow lived to about 11 years old.

Tree Swallow Population

It is estimated that around 20 million of these birds are currently alive. The numbers appear to be stable across most of its range.

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Tree swallow FAQs (Frequently Asked Questions) 

Does the tree swallow migrate?

Yes, the tree swallow undertakes a long migration south for the winter.

How many eggs does the tree swallow lay?

The tree swallow lays up to eight eggs at a time.

How fast does the tree swallow fly?

The tree swallow has a normal flight speed of 5 to 19 miles per hour, but it can also fly faster in short bursts.

What is the tree swallow’s wingspan?

The tree swallow has a wingspan of approximately 12 to 14 inches. This is more than twice the size of its actual body.

When do tree swallows leave the nest?

The tree swallow leaves the nest a few weeks after hatching.

Are tree swallows aggressive?

Tree swallows can be surprisingly aggressive for their size, especially in large flocks. They may attempt to drive off intruders or predators much larger than themselves.

Do tree swallows eat mosquitoes?

The tree swallow does eat mosquitoes, but this is just one of many insects it consumes.

How do you attract a tree swallow?

Tree swallows will be happy to take up occupancy in an artificial nest box right near your house. So long as they have a sufficiently large hole and enough protection from predators, the nest boxes will attract tree swallows (or similar species) right before the breeding season begins in the spring. Tree swallows are particularly attracted to berries, and there should ideally be a source of water nearby.

What does a tree swallow eat?

Most of the tree swallow’s diet consists of insects, berries, and seeds.

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  1. Animals Diversity Web, Available here:
  2. Audubon, Available here:
  3. Laura Erickson's For The Birds, Available here:

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