SWALLOWS: Hirundinidae

PHYSICAL CHARACTERISTICS

Swallows are distinguishable by their long, sleek tails and wings. Their gaping bill and long tails and wings are built for the long-term flight and maneuverability that enables them to catch their major source of food, flying and water-skimming insects.

Most swallows have black, brown, iridescent blue, or iridescent green plumage on top with a lighter tan, dark orange, or white chest. Their long tails may be forked (like the barn swallow) or straight across (like a cliff swallow), and act as an aerial rudder, or guide.

The legs and feet of the swallow are short and built primarily for perching, not walking. The average size of a swallow ranges from 4.75 to 8 inches (12.0 to 20.3 centimeters) in length, and they weigh from 0.4 to 2.1 ounces (10 to 60 grams).

GEOGRAPHIC RANGE

The majority of swallow species are found in Africa, but one can find swallows on virtually every major continent, except Antarctica and the high Arctic. They are also absent from New Zealand and other oceanic islands.

HABITAT

Swallows seek breeding grounds that have a good supply of flying and/or water-skimming insects, such as areas near lakes, ponds, rivers, streams, and wetlands. The species that build mud nests, such as cave and cliff swallows, also seek areas where mud is plentiful. Other species have specific requirements based on their nesting habits. During nonbreeding seasons, the majority of North American swallows, like the purple martin, migrate to the warmer climates of Central and South America.

DIET

While tree swallows will eat berries (particularly waxy bayberries) and fruits, most swallow species subsist entirely on flying and water-skimming insects such as beetles and flying ants. Purple martins will eat bigger insects as large as a butterfly, and other species also eat spiders and swarming insects like midges and mosquitoes. Virtually all insects are eaten in flight, and sometimes on the surface of the water. Swallows can even drink in flight by dipping their bills into the water as they fly across a pond or lake.

BEHAVIOR AND REPRODUCTION

Most swallows form monogamous (muh-NAH-guh-mus) pairs. Some species build their nests either in natural or human-made holes, such as tree crevices or nesting boxes. Other species use mud pellets carried by the bill-full to create nests in caves or under human-made overhangs, such as bridges. Migrating species of swallows travel in huge flocks to warmer climates in the winter, and return with the warm weather and hatching insect population.

SWALLOWS AND PEOPLE

Most swallows have a good relationship with their human neighbors. They are attractive birds that adapt well to habitat changes imposed by humans. While some people may consider a mud nest in their eaves or on their front porch a nuisance, the swallows' appetite for flying insects can help keep the pest population down.

APARTMENT DWELLERS

North American purple martins that live east of the Rocky Mountains rely exclusively on human-made "apartment-style" martin houses for nesting. The practice began hundreds of years ago when Native Americans hung hollow gourds for the birds to nest in. Western purple martins are not colonial and typically nest in tree cavities, although some will use solitary nesting boxes if available.

CONSERVATION STATUS

There is one Critically Endangered, facing an extremely high risk of extinction, species of swallow, the white-eyed river-martin. There are estimated to be fewer than fifty adults of the species, and the bird, which is native to Thailand, has not been sighted in twenty years and therefore may already be extinct. Their decline has been caused by hunting, habitat destruction, and deforestation.

Four species classified as Vulnerable, facing a high risk of extinction, are also noted by the World Conservation Union (IUCN): the blue swallow, white-tailed swallow, Bahama swallow, and golden swallow. Habitat loss due to deforestation and agricultural land use has been particularly destructive to cavity nesting and grassland-dwelling swallows.

BARN SWALLOW (Hirundo rustica): SPECIES ACCOUNTS

Physical characteristics: The barn swallow has iridescent dark blue plumage on its back, with a dark orange throat and orange to buff breast, although there are some coloring variations among the six subspecies of the bird. It is the only species of swallow that has a long, deeply forked tail. The average size of the barn swallow is 7.5 in (19 cm) long with a weight of .6 oz (17 g).

Geographic range: During the summer months, barn swallows can be found throughout North America. The birds have the most widespread range of any swallow species, and are also found throughout Europe, Asia, Myanmar, Israel, and northern Africa. North American barn swallows winter in Central and South America, while their European and Asian counterparts migrate to central and southern Africa and south and Southeast Asia.

Habitat: During breeding season, barn swallows settle in habitats with abundant insects and some access to wet earth (such as from riverbanks or drainage ditches). They build their cone-shaped, open-topped mud nests in sheltered natural areas, including cliff overhangs and caves. They also quite frequently choose human-made structures to house their families, creating nests in the rafters of barns, the underside of highway overpasses, and the eaves of other buildings.

Because of their abundant insect population, farms make ideal places for barn swallows to live, and the birds can frequently be seen flying close to crops feeding on insects. Along with feathers, the straw and mud that are found in livestock areas also make excellent building materials for a barn-based nest. Barn swallows migrate towards warmer climates in the winter, and can be found in drier climates, such as the desert, when nesting isn't a priority.

Diet: Barn swallows feed on flying insects.

Behavior and reproduction: Barn swallows return to the same area each year to breed, hatch, and fledge, raise until they can fly, their young. Often, they will use the same nest year after year if it remains intact. Building a mud nest may take anywhere from a week to a month, and both male and female work together, using thousands of mud pellets carried one by one in their bills. Straw and grass are also used, and the nests are lined with feathers. Barn swallow nests hold three to six eggs, and both female and male may share incubation duties, sitting on the eggs to keep warm. The birds are colonial, meaning that they often build nests in groups; however, males will defend their nest vigorously from both predators, animals that hunt them for food, and other barn swallows.

Barn swallows and people: Because of their appetite for flying insects that annoy, destroy vegetation, and can carry disease, barn swallows are popular neighbors, particularly to farmers.

Conservation status: Barn swallows are abundant, and not considered threatened. ∎

AMERICAN CLIFF SWALLOW (Hirundo pyrrhonota): SPECIES ACCOUNTS

Physical characteristics: American cliff swallows have a long square tail, black to blue back, rust-colored throat and rump, white forehead spot, and white to buff underside. They average 5.1 in (13 cm) in length and 0.8 oz (22.7 g) in weight.

Geographic range: This species breeds throughout North America and migrates to Central and South America in the winter.

Habitat: The cliff swallow builds its mud nest in covered areas such as the underside of cliffs and on the outside of overhanging human-made structures. They are found in a wide variety of biomes where water is available, and even in desert areas near towns and human-made construction. The nests are typically built in colonies, and unlike the barn swallow nest, they are completely enclosed with a small hole for coming and going.

Diet: American cliff swallows feed on insects while the birds are flying.

Behavior and reproduction: Cliff swallows are monogamous, migrating birds. They return to their mud nests annually to lay a clutch of three to six eggs, which they incubate for about two weeks. The brood leaves the nest approximately three weeks after hatching. Some cliff swallows are parasitic, and will lay their eggs in other cliff swallow nests within their colony to be incubated and raised by the other birds.

American cliff swallows and people: Human-made structures like bridges and dams provide an attractive spot for many cliff swallow colonies and in this sense the birds have benefited from development and construction.

Conservation status: American cliff swallows are common and are not considered threatened. ∎

CRAG MARTIN (Ptyonoprogne rupestris): SPECIES ACCOUNTS

Physical characteristics: Crag martins are an average of 5 in (14 cm) in length. They are brown on top with a dusky color on the throat and belly and dark under the wing. When they fan their squared tails, white spots are visible.

Geographic range: The crag martin breeds in mountainous areas of Europe and Asia, and migrates to the Middle East and Africa. Spain and Portugal have the largest European population, the birds are also found on some Mediterranean islands. Some varieties of crag martin are resident, meaning that they do not migrate.

Habitat: Crag martins prefer to breed in mountainous areas, but like other mud-nest dwelling swallows, can be found in virtually any biome that has a plentiful insect population and offers supplies for nest building during breeding season. Crag martin mud nests are open and are constructed under cliff edges or human-made overhangs.

Diet: The crag martin feeds on flying insects.

Behavior and reproduction: The female crag martin incubates her clutch of three to five eggs. Once the eggs are hatched, both parents feed the chicks.

Crag martins and people: Habitat destruction through development could negatively impact the crag martin, but like other mud-nesters of the swallow family, the species has proven itself very adaptable by building their homes on human-made structures.

Conservation status: Crag martins are plentiful throughout Europe and Asia. ∎

FOR MORE INFORMATION

Books:

Alderfer, Jonathan. "Swallows." In Reference Atlas to the Birds of North America. Edited by Mel Baughman. Washington, DC: National Geographic Press, 2003.

Sibley, David Allen. National Audubon Society: The Sibley Guide to Birds. New York: Alfred A. Knopf, 2000.

Periodicals:

Milius, S. "Birds May Inherit Their Taste for the Town." Science News (Dec 23, 2000): 406.

Web sites:

"Barn Swallow." All About Birds. Cornell Lab of Ornithology. http://birds.cornell.edu/programs/AllAboutBirds/BirdGuide/Barn_Swallow_dtl.html (accessed on May 28, 2004).

"Swallows: Barn Swallows in Battery Pensacola." National Park Service: Gulf Islands National Seashore. http://www.nps.gov/guis/extended/FLA/Nature/Swallow.htm (accessed on May 28, 2004).

"Attracting and Managing Purple Martins." Purple Martin Conservation Association. http://www.purplemartin.org/main/mgt.html (accessed on May 29, 2004).