SWIFTS: Apodidae

PHYSICAL CHARACTERISTICS

Swifts are aerial birds, meaning that they spend much of their lives in the air. Birds eat, drink, mate, and are believed to sleep while flying. Swifts are powerful flyers because they have strong breast muscles and long wings that are large and narrow. Their legs and feet are so small that they cannot walk. When swifts are on the ground, they are unable to quickly take off and fly. As a result, swifts land on tall trees or structures like chimneys. Swifts cling to surfaces by using their four strong toes on each foot.

The head to-tail length of swifts ranges from 3.4 to 9.6 inches (9 to 25 centimeters), and they can weigh from 0.2 to 7.6 ounces (5 to 205 grams). Most birds have black feathers, with some brown and blue coloration. Some birds have white rumps, chests, and bellies. Male and female birds have similar plumage (feathers).

The swift has a narrow body and a large head with large eyes. The bird has a short bill and a large gape, which is the width of the open mouth. The gape, being as large as the swift's head, allows it to catch and swallow insects while flying.

The word "swift" means fast, and swifts can fly at a speed of more than 100 miles (160 kilometers) per hour!

GEOGRAPHIC RANGE

Swifts are found throughout most of the world, on every continent except Antarctica.

HABITAT

Swifts' habitats vary from coniferous and deciduous forests to grasslands where there are few trees.

Swifts need to build nests in locations where it is easy for them to take flight. Swiftlets build nests in caves. Some birds make nests on cliffs, in chimneys or other tall structures.

DIET

Swifts are insectivores, animals that eat insects. Flying swifts catch and eat insects including flies, ants, beetles, and sometimes spiders. Adults eat one to three times an hour, and some birds eat ten thousand insects a day.

BEHAVIOR AND REPRODUCTION

Swifts become active at dawn. They are noisy and live in large groups called colonies. Some species migrate, flying from an area with harsh winter weather to a warmer climate where there is a larger food supply.

Swifts are monogamous (muh-NAH-guh-mus), mating with one partner. Birds make nests out of twigs, feathers, and items they find while flying. To hold the material together, swifts use their saliva, the liquid solution in their mouths, which hardens around the nest material.

The female swift lays one to six eggs. Both parents incubate the eggs, sitting on them to keep them warm in order for them to hatch. Eggs hatch in nineteen to twenty-eight days. Both parents feed the young. Other swifts, called cooperative breeders, may assist the parents in feeding. The adults carry insects for the young in pouches located below their tongues.

Cave swiftlets use only saliva when building their nests. People in Asia take the nests of some swiftlets and use them as the main ingredient in bird's nest soup. Since caves are dark, cave swiftlets use echolocation (eck-oh-loh-KAY-shun) to guide them as they move around in the caves. The birds make a sound and listen to the echoes that bounce off the surfaces.

WAITING OUT THE BAD WEATHER

Swifts depend on the weather for their food supply. They rely on breezes to blow insects in their direction. During a storm, rain washes the insects away, depleting the swifts' food supply. Cold weather also decreases the number of insects for the birds to feed on. For swift nestlings too young to fly, the solution is becoming torpid. Nestlings enter torpor, a state in which their body temperature drops and their heartbeat slows. In this state, birds can go for ten days without food.

SWIFTS AND PEOPLE

People harvest swiftlet nests for use in bird's nest soup. Bird watchers enjoy watching colonies of swifts fly across the sky. Some people track their migration and report the birds' progress on the Internet.

CONSERVATION STATUS

The World Conservation Union (IUCN) lists several species as threatened. The Guam swiftlet is Endangered, facing a very high risk of extinction, dying out. The bird population dropped by 80 percent after birds were killed by pesticides, chemicals that were sprayed to eliminate insects. Their populations have also declined due to being preyed on by the brown tree snake, a species introduced to Guam from ships by accident. The birds, being unable to take flight quickly from the ground, were vulnerable to this ground-dwelling snake.

IUCN ranks some swift species as Vulnerable, facing a high risk of extinction. Low populations make the dark-rumped swift, Aitu swiftlet, and the Polynesian swiftlet Vulnerable. Loss of habitat as trees are cut down makes the Congo swift Vulnerable. The Seychelles swiftlet is Vulnerable because birds nest at only three locations.

CHIMNEY SWIFT (Chaetura pelagica): SPECIES ACCOUNTS

Physical characteristics: The chimney swift is often described as a "cigar with wings." The swift's cylindrical body looks like a cigar. Its plumage is sooty brown (black-brown), and its underparts are gray-brown. The bird's wings are slightly curved and the tail only shows when it is spread.

Chimney swifts range in length from 4.6 to 5.4 inches (12 to 14 centimeters), and weigh from 0.8 to 1.0 ounces (20 to 23 grams).

Geographic range: Chimney swifts live and breed in the United States and Canada. They are found east of the Rocky Mountains in both countries. The swifts migrate through Central America and spend winters in South American countries including Peru and Chile.

Habitat: Chimney swifts live in forests and in cities. Birds once nested in hollow trees, but they now build nests in empty chimneys, well shafts, silos, and sometimes in building attics. Nests are located just below the opening of the structure.

Diet: Chimney swifts eat flying insects such as flies, ants, and beetles. They sometimes eat spiders.

Behavior and reproduction: Chimney swifts are sociable and travel with a colony. Birds may stay in the air until they are ready to nest.

These birds are monogamous. In the nesting season, chimney swifts build nests with twigs that they break from trees. They use saliva to attach the nest vertically (with the opening lengthwise) to the side of a hollow tree or chimney.

The female lays two to seven eggs between May and July, and the eggs hatch within nineteen to twenty-one days. Chicks fledge (grow flying feathers) in twenty-eight to thirty days. The young swifts may leave the nest a week before growing their feathers.

Chimney swifts and people: People have long watched the swifts fly south for the winter. In addition, the North American Chimney Swift Nest Research Project in Texas is tracking the birds' migration. The group wants to develop towers where swifts can roost.

Conservation status: Chimney swifts are not in danger of dying out. ∎

AFRICAN PALM SWIFT (Cypsiurus parvus): SPECIES ACCOUNTS

Physical characteristics: The African palm swift is about 6.1 inches long (16 centimeters) and weighs from 0.4 to 0.5 ounces (10 to 14 grams). The palm swift has gray-brown plumage. The head and wings are darker than the pale under parts, and some birds have streaks of color on their throats. In male birds the throat is whiter than in female swifts.

Geographic range: African palm swifts live in sub-Saharan Africa, south of the Sahara Desert. These nations include Namibia, Madagascar, and South Africa.

Habitat: African palm swifts live in grassland and other areas where there are palm trees. Birds build nests on the underside of palm leaves, and sometimes on structures like bridges.

Diet: African palm swifts eat insects, flying ants, beetles, termites, and spiders.

Behavior and reproduction: African palm swifts are active during the daytime and return at sunset to their nests in the leaves of palm trees. Birds mate and nest on the underside (back) of palm fronds.

These swifts build nests with feathers that they collect while flying, and use saliva to attach the feathers to the palm. The nest is a vertical platform. During the night, the male and female birds roost (rest). They hold onto the nest with their toes when they mate.

The female goes to the top of the platform to lay eggs. After laying an egg, she pushes it into the nest and "glues" it to the palm leaf with her saliva. She then lays another egg and repeats the process.

The female lays a clutch of one to three eggs. The eggs hatch in about twenty days. Young palm swifts fledge, or grow feathers in thirty-one to thirty-three days.

Risks to palm swifts include loss of habitat when people strip (remove) palm leaves.

African palm swifts and people: African palm swifts eat insects that people regard as pests, and the birds are a tourist attraction in Namibia.

Conservation status: African palm swifts are not in danger of extinction. ∎

FOR MORE INFORMATION

Books:

Attenborough, David. The Life of Birds. Princeton, NJ: Princeton University Press, 1998.

Baicich, Paul J., and Colin J. O. Harrison. A Guide to the Nests, Eggs and Nestlings of North American Birds. San Diego, CA: Academic Press, 1997.

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

Wells, Diana. 100 Birds and How They Got Their Names. Chapel Hill, NC: Algonquin Books, 2002.

Web sites:

North American Chimney Swift Nest Research Project. http://www.concentric.net/~dwa/page6.html (accessed on May 26, 2004).

"Palm Stripping Destroys Swifts' Nesting Places." The Free Press of Namibia (February 27, 2003) Online at http://www.namibian.com.na/2003/February/environment/03B8B156C8.html (accessed on May 26, 2004).