Apodidae

Apodidae (swifts, swiftlets; class Aves, order Apodiformes) A family of medium to small birds that have small, short bills and a wide gape. They have long, curved, narrow wings, a short tail, often square-ended or spine-tipped, some with white rumps or bellies, and short, weak legs with reversible hallux. They are highly aerial, fast-flying, and insectivorous (the 21 species of Collocalia (swiftlets), of south-east Asia, Australia, and the islands of the Indian and Pacific Oceans, use echo-location to fly in darkness). Their nests are built on trees, buildings, rocks, and in caves, often using saliva. Apus horus (horus swift) nests in sand burrows. Many authorities do not recognize the genera Hirundapus, Raphidura, Telacanthura, and Zoonavena, including them within the genus Chaetura, eight species of small, bluish-black or brown swifts, with paler throats or rumps, and spine-tipped tails, found in America. There are 12 or more genera in the family, containing about 80 species. Nearly all are tropical, northern-breeding birds migrating to the tropics in winter, but they are found world-wide. The 15 Apus species are found mainly in Africa, but also in Europe, Asia, and Australia.