Swifts

Swifts are a family of highly aerial birds known as Apodidae, which reside within the Apodiformes order alongside hummingbirds. They resemble swallows due to convergent evolution, as both hunt insects on the fly, but they are not closely related. Swifts have small, weak legs, which led to them sometimes being depicted without feet historically. Their classification is complex, with some fossil evidence suggesting they appeared during the Eocene period. There are about 100 species of swifts, which are known for their high speeds, with the white-throated needletail reaching up to 169 km/h. They have elongated wingtip bones and the ability to rotate their wings from the base, which aids in their maneuverability and efficiency in flight. Swiftlets have evolved a form of echolocation to navigate dark caves. These birds are found worldwide except in the extremes of the polar, desert, and some oceanic islands, and migratory swifts travel from temperate regions to the tropics in winter. Their nests, often attached to vertical surfaces with saliva or located in wall cavities, are unique—some are used in the traditional bird's nest soup. Swifts are insectivores, hunting mid-flight, and their breeding and development patterns are more similar to seabirds than passerines. While no swift species has been recorded as extinct since 1600, some are considered endangered or vulnerable due to factors including habitat loss and overharvesting of their nests by humans for culinary purposes.