TREE SWIFTS: Hemiprocnidae

PHYSICAL CHARACTERISTICS

The head-to-tail length of tree swifts ranges from 5.8 to 11.5 inches (15 to 30 centimeters). Birds weigh from 0.8 to 2.9 ounces (21 to 79 grams). Tree swifts have long wings and tails that are forked and divided into two sections so that they resemble the letter V turned on its side. Tree swifts fly quickly when hunting food, but they live in one area and usually do not migrate.

Tree swifts belong to the Apodiformes order that also includes swifts and hummingbirds. While all the birds share some physical characteristics, swifts and hummingbirds have weak feet and do little perching, sitting or standing on a surface. Instead, they spend much of their time in the air. Tree swifts have stronger legs and are able to perch in trees.

Swifts have mostly gray plumage, feathers. Tree swifts and hummingbirds are more colorful. Tree swifts have patches of color in their plumage. Some birds have whiskers. Other birds have a crest, a group of feathers that stand upright on their foreheads.

Some species characteristics are described by the birds' names. The crested tree swift has a crest. The gray-rumped tree swift has gray plumage on its rump. The moustached tree swift has a white "moustache," white plumage that extends from the chin to the back of the neck. The whiskered tree swift has long feathers that extend from the face like whiskers. The bird is also known as the lesser tree swift.

GEOGRAPHIC RANGE

Tree swifts live in Asia in the countries of India, Nepal, Sri Lanka, Malaysia, Bangladesh, Myanmar, Thailand, Bali, China, Cambodia, and Vietnam. They also range in New Guinea, Bismarck, the Philippines, and the Solomon Islands.

HABITAT

Tree swifts live in various types of tree habitats. They live in forests with deciduous trees that lose their leaves during cold or very dry seasons. Tree swifts also live in forests with coniferous or evergreen trees that generally stay green all winter. They range in rainforests where abundant rainfall produces a lot of growth. The birds also range in grassland areas called savannas where there are fewer trees and grasses grow. They range near forest openings and are sometimes found near the edge of rivers. Some species also live in towns and are found in gardens.

DIET

Tree swifts eat flying insects like ants, beetles, wasps, and bees. Tree swifts are aerial feeders; they fly after prey, insects hunted for food. The birds also eat spiders.

BEHAVIOR AND REPRODUCTION

Tree swifts are usually sedentary, staying in one area throughout the year. Birds roost, rest, during the daytime and perch standing up on branches. Tree swifts are crepuscular (kri-PUS-kyuh-lur) and nocturnal; they become active at twilight or in the evening.

Tree swifts form small groups, but they have been seen in flocks of up to fifty gray-rumped tree swifts. Birds flock to chase flying insects.

SOCIAL SWIFT SPECIES

Some tree swift species are more social than others. Crested tree swifts form groups of six to twelve birds. They have little to do with other species. Whiskered tree swifts may be alone, in pairs, or in groups of six birds. However, the whiskered birds do not mind sharing their tree with gray-rumped tree swifts. Gray-rumped tree swifts just perch higher in the trees, which probably helps the two species get along.

Tree swifts are monogamous (muh-NAH-guh-mus), they have only one mate. Tree swifts build tiny nests out of feathers and pieces of bark. Like other Apodiformes, tree swifts build nests with saliva, the watery liquid in their mouths. Their salvia hardens as it dries, so swifts use saliva to glue the saucer-shaped nest together. The female lays one egg. Both parents incubate the egg, keeping it warm, until it hatches after approximately three weeks. Birds fledge, grow feathers needed for flight, about three weeks later.

Predators that hunt tree swifts for food include snakes and larger birds.

TREE SWIFTS AND PEOPLE

People enjoy watching flocks of tree swifts. Gray-rumped birds are active at dusk and can be seen flying down to drink from pools and other bodies of water.

CONSERVATION STATUS

Tree swifts are not in danger of extinction, dying out.

CRESTED TREE SWIFT (Hemiprocne coronata): SPECIES ACCOUNT

Physical characteristics: Crested tree swifts range in length from 8.2 to 9 inches (21 to 22.6 centimeters) and weigh 0.7 to 1.0 ounces (20 to 26 grams). They have long, narrow wings and forked tails. All birds have blue-gray plumage, green-blue crests on their foreheads, and coloring that looks like black eye patches.

Male crested tree swifts have a pale rufous, brownish red, patch below the eye. That coloring extends to ear coverts, small feathers near the ears. On male bodies, feathers are white below the breasts. Wings are mainly blackish brown. Some wing feathers are pale gray and blue. Tails are blue-gray on top and pale gray on the back side.

Female crested tree swifts have black plumage in the area between their eyes and bills. That black coloring extends to their ear coverts. Below the black plumage is a thin line of white plumage that looks like a moustache. The line extends from the face to the sides of the head below the ears. Female crested tree swifts have dark gray throats.

Crested tree swifts were once thought to belong to the same species as the gray-rumped tree swift. However, the crested swifts do not have pale gray plumage on their rumps.

Geographic range: Crested tree swifts live in India, Nepal, Sri Lanka, Bangladesh, Myanmar, Thailand, China, Cambodia, and Vietnam.

Habitat: Crested tree swifts live in deciduous forests, in open areas near trees, and in home gardens. Most birds live in areas with altitudes, heights, of no more than 1,197 feet (365 meters). However, birds also range at higher altitudes of 3,937 to 4,593 feet (1,200 to 1,400 meters).

Diet: Crested tree swifts eat flying insects like the small, two-winged midge.

Behavior and reproduction: While crested tree swifts are sedentary, don't migrate, the birds in India sometimes fly to different parts of the country when seasons change. Crested tree swifts are nocturnal and are active in the later part of the night. Birds look for food in pairs or in small groups of six to twelve birds. They fly in circles to feed, and their call is described as harsh.

Crested tree swifts often perch upright on branches with no leaves. They have favorite perches and stand with the tips of their wings crossed.

The breeding season varies by location, but birds usually mate between December and July. The male and female birds build a tiny nest out of pieces of bark, feathers, and saliva. Birds attach the nest to a branch with saliva, and the female lays one gray egg. Both parents incubate the egg. They do this by perching upright and covering the egg with their feathers.

The egg hatches after about three weeks. Both parents care for the chick. The young bird fledges approximately fifty days after the egg was laid.

Crested tree swifts and people: Since the crested tree swift population is large and found in many countries, they are often studied to learn more about the family.

Conservation status: Crested tree swifts are not at risk of extinction. ∎

FOR MORE INFORMATION

Books:

Ali, Sálim. The Book of Indian Birds. Oxford, U.K.: Oxford University Press, 1996.

Chantler, Phil. Swifts: A Guide to the Swifts and Tree Swifts of the World, 2nd ed. New Haven, CT: Yale University Press, 2000.

Kennedy, Robert S., et al. A Guide to the Birds of the Philippines. Oxford, U.K.: Oxford University Press, 2000.

Robson, Craig. Birds of Thailand. Princeton, NJ: Princeton University Press, 2002.

Web sites:

Lockwood, Burleigh. "Apodiformes." Chaffee Zoological Gardens of Fresno. http://www.chaffeezoo.org/animals/apodiformes.html (accessed on June 25, 2004).