Footless-looking flyers faster than most birds
Apodidae swifts share the sky with swallows but not their family tree; they sit with hummingbirds in Apodiformes. The Greek ápous—“footless”—mocks their tiny legs. Large needletails have been timed near 169 kilometres per hour, and a common swift may log two million kilometres in a lifetime.
Convergent aerial hunting explains the swallow look-alike shape. About one hundred species fall into two subfamilies and four tribes, though genus lines—especially among swiftlets—remain contested because behavior, morphology, and DNA often disagree. Apodiform diversity bloomed in the Eocene; fossils such as Scaniacypselus and Procypseloides turn up across temperate Europe. Treeswifts form the related family Hemiprocnidae.
Wings can reshape mid-flight by changing angles between tip and forearm bones, and like hummingbirds they rotate the wing from the base for fine control. Cave swiftlets navigate dark roosts by echolocation; the three-toed swiftlet even uses the trick outside at night. Ranges skip Antarctica, the high Arctic, big deserts, and many oceanic islands; temperate breeders winter in the tropics, and some species briefly enter torpor in cold snaps. Size spans the 5.4-gram, nine-centimetre pygmy swiftlet to far larger needletails with crescent boomerang silhouettes.
Many glue nests to vertical faces with saliva; Aerodramus nests are pure saliva and the stock for bird’s-nest soup, harvested for over four hundred years from edible-nest and black-nest swiftlets, with over-collection driving declines. Eggs hatch after nineteen to twenty-three days; young fledge six to eight weeks later with both parents feeding. Clutches are smaller and development slower than in similar-sized passerines, and chicks can briefly outweigh adults. Several swiftlets and the chimney and American black swifts rank as vulnerable on BirdLife lists.
Source: Swift (bird)
