Swiftlets are small birds belonging to the family Apodidae, known for their remarkable flying abilities. They are primarily found in tropical and subtropical regions of Asia, where they inhabit caves and cliffs. Swiftlets have a unique adaptation: they can produce a special type of nest made from their saliva, which hardens when exposed to air. These nests are highly valued in some cultures, particularly in Chinese cuisine, where they are used to make bird's nest soup. Swiftlets are also known for their echolocation abilities, allowing them to navigate in dark environments. Their diet mainly consists of insects, which they catch while flying.