Swift, a family of birds noted for their exceptionally fast flight. In appearance swifts resemble swallows, but they are not related. Swifts are found practically throughout the world. There are about 65 species, ranging in length from about 3 ½ to about 8 inches (9 to 20 cm). Some of the smaller species are called swiftlets. Swifts are predominantly brownish or blackish, often with lighter markings. Their thin, pointed wings curve backwards. Swifts spend most of their time in the air, eating insects they catch in flight.
Swifts have short feet and rarely perch on trees or rest on ground. They roost clinging upright on vertical surfaces. During nesting season, swifts develop large salivary glands. They use the saliva to glue their nest material, usually bits of vegetation, together. Certain species of cave swiftlets, native to Asia, make their nests almost entirely of saliva. The nests of these swifts are used to make bird's-nest soup. The eggs are white and the number ranges from one in some species to four or six in others. Both parents incubate the eggs and feed the young.
Well-known swifts include the chimney swift of eastern North America and the common swift of Europe. Chimney swifts are blackish and about 5 inches (13 cm) long. They breed from Canada south to the Gulf of Mexico, and winter in South America, where they migrate in large flocks. As their name implies, these swifts often build their nests in chimneys. Common swifts breed in most parts of Europe. They are about 6 ½ inches (17 cm) long. These blackish birds also migrate south in winter. They nest in holes in cliffs and under the eaves of buildings.
Swifts make up the family Apodidae. Cave swift-lets are of the genus Collocalia. The chimney swift is Chaetura pelagica; the common swift, Apus apus.