Tree swallows are small, migratory songbirds found throughout North America. They are aerial insectivores, meaning they catch insects while flying. Identifying tree swallows is easiest during summer when they are most widespread across the continent. Their key identifying features include their glossy, iridescent plumage, white undersides, and narrow, pointed wings.
What do tree swallows look like?
Tree swallows are petite songbirds, measuring around 5-6 inches in length with wingspans of 11-13 inches. They have slender, streamlined bodies and long, pointed wings. Their tails are slightly forked. Tree swallows exhibit sexual dimorphism, meaning males and females have different plumage. Adult males are iridescent royal blue-green on the back and upperparts. Their heads are blackish with a blue sheen. Females and juveniles are less vividly colored, with duller brownish upperparts and lighter underparts. All tree swallows, regardless of age or sex, have clean white undersides from chin to belly and crisp white patches above the eyes.
Color Patterns
The iridescent sheen on a male tree swallow’s back can appear blue, green, or purple depending on the angle of the light. Females and juveniles often show more green iridescence. The white patches on the face contrast sharply with the blackish head. The rump is white. The tail and flight feathers are sooty brownish-black. The underparts are snowy white from the throat down to the crisply defined border separating the white breast and belly from the darker back and wings.
Size and Shape
Tree swallows have very slender, streamlined bodies with long, pointed wings. Length ranges from 5.1-6.3 inches. Wingspans stretch 11-13 inches across. Compared to other swallows, tree swallows have longer, more triangular wings and shorter tails. The tail is slightly forked at the tip. Legs and feet are tiny and adapted for perching rather than walking. Overall shape in flight is graceful, buoyant, and nimble.
Where are tree swallows found?
Tree swallows breed across North America from Alaska to central California east to Newfoundland and south to Florida. They migrate to spend winters along the U.S. Gulf Coast, Mexico, Central America, and the Caribbean islands. Summer range covers open habitats across most of Canada and the continental United States south to New Mexico and South Carolina.
Breeding Range
The core breeding range includes Canada and the northern U.S. from the Pacific to Atlantic coasts. Tree swallows nest as far north as central Alaska and the southern Yukon Territories. To the south, they breed south to central California, Arizona, New Mexico, and western Texas. Eastward, the range extends across the U.S. into the Midwest and Northeast, including all the New England states north to Newfoundland and Labrador.
Wintering Range
Tree swallows are long-distance migrants, wintering along the U.S. Gulf Coast from Florida to Texas, farther south throughout Mexico into Central America, and throughout the Caribbean islands. Northern populations migrate the farthest distances, traveling thousands of miles between their wintering and breeding grounds. Birds from the southernmost breeding areas may only migrate short distances.
Year-Round Range
Small populations of tree swallows in Florida and along the Gulf Coast may reside there throughout winter. Tree swallows are also expanding northward along the Pacific Coast, with increasing numbers reported through winter in Washington’s Puget Sound region.
What kind of habitats do tree swallows prefer?
Tree swallows thrive in open habitats near water, fields, wetlands, lakes, and rivers. They readily adapt to nesting around human structures and are attracted to nest boxes.
Fields and Meadows
Tree swallows forage over open habitats like meadows, pastures, agricultural fields, prairies, and grasslands. They avoid dense forests and urban centers.
Wetlands
Tree swallows frequently feed over marshes, swamps, ponds, and other wetlands where flying insect prey is abundant.
Lakes, Rivers, Streams
Bodies of fresh water, including lakes, rivers, creeks, and streams, provide reliable food resources for aerial-feeding tree swallows.
Coastlines
Coastal areas, especially salt marshes, estuaries, and bays are also prime feeding grounds for tree swallows.
Nest Sites
Tree swallows nest in cavities in dead trees, rock crevices, and man-made nest boxes in open country. They readily take to nest boxes including birdhouses, reducing reliance on natural nest sites. Nest boxes should be placed facing open habitat over 10 feet off the ground.
What do tree swallows eat?
Tree swallows are aerial insectivores. They catch all their prey while flying. Their diet is mostly small flying insects like flies, beetles, moths, bees, wasps, mayflies, and damselflies. They also eat flying ants and other winged insects.
Flying Insects
Tree swallows eat a wide variety of small flying insects, primarily flies, midges, mosquitoes, mayflies, dragonflies, damselflies, caddisflies, butterflies, moths, grasshoppers, flying ants, bees, wasps, and beetles.
Aerial Feeding
Tree swallows catch insects while flying. They sally forth from perches and feed in swarms over open country. swallows feed in continuous flight except when stopping to gather nest material or rest.
Spring through Fall Feeding
Food is caught and eaten on the wing from spring migration through fall departure for wintering grounds. Peak feeding occurs during the breeding season when nutritious insects are needed to produce eggs and raise nestlings.
Non-Flying Prey
Tree swallows very rarely eat anything besides flying insects. On rare occasions, they may eat spiders ballooning on threads or steal eggs from other birds’ nests.
What are the features that distinguish tree swallows from other swallows?
Tree swallows differ from other North American swallows in their color patterns, body shape, habitat preferences, and behaviors.
Color Patterns
Male tree swallows are glossy iridescent blue-green above with strongly contrasting blackish heads and crisp white underparts. Females are paler and greener. The white rump patch, face patch over the eyes, and sharply defined white breast/belly border aid identification.
Body Shape
Tree swallows have a classic swallow shape – slender, streamlined and built for flight – but with longer, more pointed wings and shorter tails than other swallow species.
Habitat
Tree swallows favor open country near water rather than cities and towns. They nest in cavities in dead trees rather than colonial mud nests. Other swallows breed in more urban areas and nest on bridges and buildings in large colonies.
Behavior
Tree swallows are scrappy and aggressive compared to other swallows. They fiercely compete for nest sites. They do not breed in dense colonies. Nest spacing averages 50-100 yards apart even in optimal habitat.
Swallow Species | Key Differences from Tree Swallows |
---|---|
Barn Swallow | Dark blue back; deeply forked, elongated tail; breeds on ledges and beams in barns and other manmade structures; colonial nester |
Cliff Swallow | Pale orange rump patch; colonial mud nests on vertical cliffs and buildings; Stockier build with shorter wings |
Bank Swallow | Plain brown back; small bandit mask; digs nesting burrows in dirt banks and bluffs; more social nester |
Purple Martin | Much larger size; entirely glossy blue-black plumage; nests in apartment-style colonies; dependent on man-made nest boxes |
When and where are tree swallows most active?
Tree swallow activity is greatest during spring and summer breeding season in temperate North America. Spring migration starts in late February and March. Birds disperse to breeding areas throughout April. Peak activity spans late spring through summer during breeding, nesting and raising young. Activity declines away from breeding areas during migration and on tropical wintering grounds.
Spring Migration: Late February to May
Spring migration begins as early as late February in the southern U.S. Flocks arrive farther north throughout March and April. Birds establish breeding territories by May at the latest.
Breeding Season: May through July
Once paired, tree swallows are busy building nests, laying eggs, incubating, and raising young through July. Both parents feed nestlings frequently from dawn to dusk.
Fall Migration: August to October
Southbound migration starts as early as late July and August for northern breeders. Southern populations may not depart until October. Many tree swallows migrate long distances in large mixed flocks with other swallow species.
On Wintering Grounds
Activity declines on wintering grounds farther south. But tree swallows remain active catching flying insects through the winter along the U.S. Gulf Coast, Mexico, Central America, and the Caribbean Islands.
What are the songs and calls of tree swallows?
Tree swallow communication consists of a variety of high-pitched, buzzy twitters, chips, and whistles. The most distinctive vocalization is the low-pitched gargling calls and rattles given by displaying males during courtship.
Display Calls
Courting males make unique gurgling and rattling sounds interspersed with twitters while pursuing females. These distinctive noises sound metallic or like the clicking of marbles colliding.
Alarm Calls
Harsh, scolding chips and chattering calls are given in alarm when threatened or defending nest sites. These calls signal danger to conspecifics.
Contact Calls
Tree swallows keep in contact with mates and offspring using short twitters and whistles while foraging and throughout the day. These high-pitched sounds communicate location.
Song
Sung primarily by males from prominent perches near the nest. Songs consist of a long, musical series of twitters, chips, trills and gurgles.
Nestling Calls
Hungry nestlings beg with a frantic series of raspy chirping calls that stimulate adults to deliver food. As nestlings mature, their calls become louder and more prominent.
How can you attract tree swallows to your yard?
You can encourage tree swallows to take up residence in your yard by providing suitable nest boxes in open habitat. Position boxes facing openings over 10 feet off the ground before spring migration. Keep nests clean and protected from predators and tree swallows may return year after year.
Nest Boxes
Put up specially designed nest boxes for tree swallows. Boxes should have 1.5 inch diameter entrance holes 5-9 feet off the ground. Face the boxes towards open habitats like lawns, meadows or water.
Habitat
Tree swallows prefer nesting where they can exit the box and have unobstructed flight paths to foraging areas. Avoid placing boxes with surroundings that are too wooded, shrubby or overgrown.
Timing
Set boxes out in desired locations by late February or early March before the start of spring migration. Early arrival at nest sites helps establish territory ownership.
Maintenance
To encourage returning pairs, keep nests clean and well-maintained. Remove old nesting material annually after breeding season. Perform any needed repairs before the next spring.
Protection
Guard nest boxes against predators. Add predator guards or barriers to deter raccoons, snakes, and other nest intruders. Monitor boxes for invasive species like house sparrows.
Conclusion
Tree swallows are elegant, aerial insect-hunting songbirds readily identified by plumage and behavior. Look for their glossy iridescent backs, crisp white undersides, buoyant flight and fierce territoriality. Provide suitable nest boxes and tree swallows will grace your yard with their swooping, acrobatic maneuvers as they hunt insects on the wing.