The family of Swifts is globally distributed except in the coldest regions. They are small birds, 9 cm to 23 cm long. The wings are long and pointed, the legs and feet are very small and the beak is small with a crooked point and a wide throat. Sails are perfectly adapted to life in the air, and some species are able to spend the night in flight and to mate. They are excellent and fast fliers, on the other hand, many species cannot take off from the ground. The nests of a few species are made entirely of saliva and are considered a delicacy in Chinese cuisine. Some species of salangan have the exceptional echolocation capability. They use this to orient themselves in underground cave systems, where their nesting sites are.