caprimulgiform

Caprimulgiformes is an order of birds traditionally comprising nightjars and their allies. The name derives from caprimulgus, the genus of the common nightjar, reflecting an old belief that these birds drank milk from goats at night. In many classifications caprimulgiformes refers to nocturnal or crepuscular, insectivorous birds with broad mouths and long wings.

The traditional composition includes five families: Caprimulgidae (nightjars), Nyctibiidae (potoos), Podargidae (frogmouths), Aegothelidae (owlet-nightjars), and Steatornithidae (oilbirds). Members are generally medium-sized, with cryptic plumage, large eyes, and a tendency to perch motionless during the day and hunt insects on the wing after dusk. Oilbirds are unusual in being largely frugivorous and, in some species, using echolocation to navigate in caves.

Physically, caprimulgiforms have broad, gaping mouths bordered by rictal bristles that help catch insects. Their wings are long and broad, enabling rapid, agile flight in low light. Vocalizations range from subdued daytime calls to high-pitched night sounds; many species are more often heard than seen.

Ecology and reproduction vary across lineages. Many species nest in simple sites, often with small clutches, and occupy habitats ranging from forests to open woodlands. Distribution is global, with nightjars and frogmouths found across Eurasia, Africa, the Americas, and Australasia, potoos in the tropical Americas and Africa, and oilbirds in the Caribbean and northern South America.

Taxonomy among caprimulgiforms has shifted with molecular data, and some authorities place the families in different orders or restructure their relationships. The term remains in use as a practical label for this nocturnal, often insectivorous, group of birds.