Tachycineta bicolortree swallow

Geographic Range

Tree swallows breed throughout central and northern North America. The northernmost limit of the tree swallow breeding range coincides approximately with the tree line. Tree swallows winter in southern North America, primarily in Florida, and along the Caribbean coast of Central America. (Robertson, et al., 1992)


Tree swallows live in open areas near water, such as fields, marshes, meadows, shorelines, beaver ponds, and wooded swamps. Because tree swallows are cavity nesters, an important habitat requirement is cavities in which to nest. These can be provided by standing dead trees, sapsucker-excavated holes in live trees, under the eaves of buildings,and in artificial nest boxes. (Robertson, et al., 1992)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

Tree swallows are small birds (14 cm total length) with long wings and small legs and feet. They are irridescent greenish-blue above and white below on the chin, breast and belly. Tree swallows have a short black beak and dark reddish-brown or brownish-gray feet.

Juvenile tree swallows are similar in appearance to adults, but are brownish rather than greenish blue. They also have a dusky wash across their white chests. One-year-old females look very similar to adults, but have a mixture of brown and irridescent greenish-blue above. (Robertson, et al., 1992)

  • Sexual Dimorphism
  • sexes alike
  • Average mass
    19 g
    0.67 oz
  • Average length
    14 cm
    5.51 in


Tree swallows are primarily monogamous. However, polygyny has been documents at low rates in some populations. Breeding pairs form as soon as females arrive at breeding sites in the spring. Extra-pair copulations are common in this species; as many as 50% of nests in a given population may contain young that were not fathered by the resident male. (Robertson, et al., 1992)

Tree swallows breed between May and September, and raise one brood per year. They usually nest solitarily, though they will nest near each other if existing cavities are close together. Nest building takes place in late April or early May. Nests are typically built in cavities in dead or live trees (excavated earlier by woodpeckers or other species) or in hollow stumps over water. However, they can also be found under the eaves of buildings, in steel drums, fire hydrants, holes in the ground or nest boxes. Nests are built almost entirely by the female. They are made of grasses, mosses, rootlets, and aquatic plants, and are lined with feathers from other species of birds. Construction takes from a few days to two weeks.

The female lays 2 to 8 (usually 4 to 7) eggs, at a rate of one per day. The female then incubates the eggs for 11 to 19 (usually 14 to 15) days. The female broods the altricial chicks for the first three days after hatching. Both parents share the responsibility of feeding and finding food for the chicks. Chicks fledge 15 to 25 days after hatching (usually 18 to 22 days), at which time they are good fliers. The parents continue to feed the chicks for at least 3 days after they leave the nest. These chicks will be able to breed the next summer if they are able to establish a nest site. (Robertson, et al., 1992)

  • Breeding interval
    Tree swallows breed once per year.
  • Breeding season
    Tree swallows breed between May and September.
  • Range eggs per season
    2 to 8
  • Average eggs per season
  • Range time to hatching
    11 to 19 days
  • Average time to hatching
    14.5 days
  • Range fledging age
    15 to 25 days
  • Range time to independence
    3 (low) days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Female tree swallows build the nest, incubate the eggs and brood the chicks. Both parents feed the chicks while they are in the nest and for at least three days after they fledge. (Robertson, et al., 1992)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female


Annual adult tree swallow survival is estimated at 40 to 60%. Estimated average life span of tree swallows is 2.7 years. However, the oldest known tree swallow lived at least 11 years. (Robertson, et al., 1992)

  • Range lifespan
    Status: wild
    8 to 11 years
  • Average lifespan
    Status: wild
    2.7 years
  • Average lifespan
    Status: wild
    145 months
    Bird Banding Laboratory


Tree swallows are highly social and may form flocks of several thousand birds at nighttime roosts outside of the breeding season. However, they are strongly territorial during the breeding season. Both sexes defend an area around their nest, usually a 10 to 15 m radius, against conspecifics and other nest site competitors. Competition for nest sites is thought to be the underlying motive behind much of tree swallow behavior, including sexually selective infanticide, frequent copulation, and strong aggressive responses to nest site competitors.

Tree swallows are fully migratory. They migrate during the day, often in loose flocks, and roost together in large groups at night.

As their name suggests, tree swallows spend little time on the ground, preferring instead to perch. They spend much of their time in flight and tend to glide more than any other species of swallows. In order to bathe, swallows swoop down over water. They lightly brush the water and then begin to fly upwards, shaking the water off. They also bathe by preening extensively during rainfall, using it as a shower. (Robertson, et al., 1992)

  • Range territory size
    3 to 700 m^2

Home Range

The size of tree swallow home ranges changes throughout the year. Before eggs are laid, tree swallows may travel up to 60 km to forage. However, during the incubation and nestling stages, tree swallows probably stay within about 5 km of the nest site. (Robertson, et al., 1992)

Communication and Perception

Tree swallows communicate primarily using sounds and physical displays. Only male tree swallows sing, apparently for the purpose of proclaiming their territory. Both sexes use calls to communicate. At least 14 different tree swallow calls have been identified. The apparent purposes of these calls range from signaling distress, anxiety, pleasure and submission to begging for food and soliciting copulation. Body signals such as crouching and wing-fluttering are used to communicate a variety of messages, including aggression and solicitation of copulation. (Robertson, et al., 1992)

Food Habits

Tree swallows primarily eat flying insects, though they also eat plant materials (about 20% of their diet). They forage in flight, in open areas above water or ground. They sometimes forage in flocks when insects are abundant. They can also glean insects from the surface of water or vertical surfaces. Swallows feed from dawn until dusk, mainly on flies, beetles and ants, though stoneflies, mayflies, caddisflies, spiders and grasshoppers are also common prey. When weather conditions are bad, tree swallows feed on vegetation, including bulrushes, bayberries, and other plants' seeds. (Robertson, et al., 1992)

  • Animal Foods
  • insects
  • Plant Foods
  • seeds, grains, and nuts
  • fruit


Tree swallow eggs and nestlings are vulnerable to predation by rat snakes, raccoons, black bears, American kestrels, common grackles, American crows, northern flickers, chipmunks, weasels, deer mice and feral cats. Adults are taken in flight by black-billed magpies and raptors, including sharp-shinned hawks, American kestrels, merlins, peregrine falcons and great horned owls.

Tree swallows respond to predators by mobbing them. Large numbers of tree swallows swarm and dive-bomb the predator while giving alarm calls. (Robertson, et al., 1992)

Ecosystem Roles

Tree swallows affect the populations of the animals they eat. They also provide food for their predators. They host a number of body parasites, including blowfly larvae. (Robertson, et al., 1992)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Tree swallows eat many kinds of insects that humans may consider to be pests.

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no known adverse effects of tree swallows on humans.

Conservation Status

Tree swallows are a relatively common birds. Global populations of tree swallows have increased over the last 25 years to an estimated 20,000,000. Tree swallows readily use nesting boxes, making them a good study species for studies of the effect of pollutant on birds. PCBs and DDE have been found to be present in high levels in adults, eggs, and nestlings. It has also been found that birds in more acidic wetlands produce fewer and smaller young. These observations may suggest a possible long-term problem for tree swallows. A more pressing consideration, however, is the maintenance of dead trees, which provide nest sites for tree swallows and other cavity-dwellers. (Robertson, et al., 1992)


Kari Kirschbaum (author, editor), Animal Diversity Web.

Jennifer Roof (author), University of Michigan-Ann Arbor, Marie S. Harris (author), University of Michigan-Ann Arbor.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map


uses sound to communicate


living in landscapes dominated by human agriculture.


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.


an animal that mainly eats meat


uses smells or other chemicals to communicate

  1. active during the day, 2. lasting for one day.

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


An animal that eats mainly insects or spiders.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


marshes are wetland areas often dominated by grasses and reeds.


makes seasonal movements between breeding and wintering grounds


Having one mate at a time.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


living in residential areas on the outskirts of large cities or towns.


a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


uses sight to communicate


Harrison, H. 1975. A field guide to the birds' nests: United States east of the Mississippi River. New York: Houghton Mifflin, Peterson Field Guide Series.

Robertson, R., B. Stutchbury, R. Cohen. 1992. Tree Swallow (Tachycineta bicolor). Pp. 1-28 in A Poole, P Stettenheim, F Gill, eds. The Birds of North America, Vol. 11. Philadelphia, PA: The Academy of Natural Sciences; Washington, DC: The American Ornithologists' Union.