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Barn Swallow Life History

Habitat

Habitat GrasslandsBarn Swallows forage in open areas throughout most of the continent, including suburban parks and ball fields, agricultural fields, beaches, and over open water such as lakes, ponds and coastal waters. They range from sea level up to 10,000 feet. Breeding habitat must include open areas for foraging, structures or cliffs to build nests on, and a source of mud such as a riverbank to provide the material for building nests.Back to top

Food

Food InsectsFlies of all types make up the majority of the Barn Swallow’s diet, along with beetles, bees, wasps, ants, butterflies, moths, and other flying insects. Barn Swallows usually take relatively large, single insects rather than feeding on swarms of smaller prey. They will also pick up grit and small pebbles, or eggshells and oyster shells set out by humans, which may help the birds digest insects or add needed calcium to the diet.Back to top

Nesting

Nest Placement

Nest BuildingBarn Swallow pairs explore a number of potential nesting spots, flying up and hovering to investigate a location, then moving to another site before narrowing their choice. Preferred sites include eaves, rafters, and cross beams of barns, sheds and stables, as well as the undersides of bridges, wharfs, and culverts. They may also use nests from previous years, but avoid those infested heavily with mites or other parasites.

Nest Description

Both male and female build the nest cup using mud. They collect mud in their bills and often mix it with grass stems to make pellets. They first construct a small shelf to sit on, then build up the nest’s sides. If built against a wall or other vertical surface the result is a semicircular, half-cup shape. Nests built on top of a beam or other horizontal surface form a complete cup about 3 inches across at the rim and 2 inches deep. The birds line the cup first with grass, then feathers, and in colonies may steal nest-lining materials from neighboring nests. When reusing nests, Barn Swallows clean out old feathers and add new mud to the nest’s rim.

Nesting Facts

Clutch Size:3-7 eggs
Number of Broods:1-2 broods
Egg Length:0.6-0.8 in (1.6-2.1 cm)
Egg Width:0.5-0.6 in (1.2-1.5 cm)
Incubation Period:12-17 days
Nestling Period:15-27 days
Egg Description:Creamy or pinkish white, spotted with brown, lavender, and gray.
Condition at Hatching:Eyes closed, naked except for sparse tufts of pale gray down.
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Behavior

Behavior Aerial ForagerWatch for the Barn Swallow’s smooth, fluid wingbeats and the way they pull their wingtips back at the end of each stroke. These birds feed almost exclusively in flight, flying lower than many other swallow species and often nearly hugging the ground or water surface. They catch flies and other prey in midair above fields, marshes, lakes, and coastal waters, and often follow farm implements, cattle herds, and humans to snag flushed insects. They occasionally feed on sluggish or dead insects on the ground, and in cold weather will pluck flies off barn walls. Barn Swallows also drink and even bathe on the wing, dipping down to take a mouthful of water or touch their belly to the surface for a quick rinse. Males defend a small territory around the nest site and aggressively chase away other males, even grabbing them with their feet and tumbling to the ground. Individuals or groups of Barn Swallows mob predators such as hawks, gulls, or grackles that approach nests.Back to top

Conservation

Conservation Low ConcernBarn Swallow populations declined by close to 0.6% per year from 1966 to 2019, resulting in an estimated cumulative decline of 25%, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 190 million and rates them 8 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. Barn Swallows were hunted for the hat trade in the nineteenth century and are still hunted for food in parts of their wintering range. Discarded twine or fishing line can pose a problem when Barn Swallows use these materials to line their nests, because the strands can entangle adults or young and trap them. On a more positive note, this species has benefited from human-made structures, and people generally encourage these attractive, insect-eating birds to nest near them. As a result, Barn Swallows have greatly expanded their breeding range and numbers as people have settled the continent.Back to top

Credits

Brown, Charles R. and Mary B. Brown. (1999). Barn Swallow (Hirundo rustica), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Ehrlich, P. R., D. S. Dobkin, and D. Wheye (1988). The Birder's Handbook. A Field Guide to the Natural History of North American Birds, Including All Species That Regularly Breed North of Mexico. Simon and Schuster Inc., New York, NY, USA.

Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.

Myers, G. R. and D. W. Waller. (1977). Helpers at the nest in Barn Swallows. Auk 94:596.

Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2019). The North American Breeding Bird Survey, Results and Analysis 1966–2019. Version 2.07.2019. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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