Owlet-nightjars are insectivores which hunt mostly in the air but sometimes on the ground; their soft plumage is a crypic mixture of browns and paler shades, they have fairly small, weak feet (but larger and stronger than those of a frogmouth or a nightjar), a tiny bill that opens extraordinarily wide, surrounded by prominent whiskers. The wings are short, with 10 primaries and about 11 secondaries; the tail long and rounded.
The comprehensive 2003 study by Dumbacher et al. analyzing mtDNA sequences Cytochrome b and ATPase subunit 8 suggests that 11 species of owlet-nightjar should be recognized, plus one that went extinct early in the second millennium AD.
The relationship between the owlet-nightjars and other groups within the Caprimulgiformes has long been controversial and obscure and remains so today: in the 19th century they were regarded as a subfamily of the frogmouths, and they are still generally considered to be related to the frogmouths and/or the nightjars but there have also been recent suggestions (Mayr, 2002) that they are not so closely related to either as previously thought, and that the owlet-nightjars share a common ancestor with the Apodiformes.
In form and habits, however, they are very similar to both caprimulgiform group - or, at first glance, to small owls with huge eyes. Interestingly, the ancestors of the swifts and hummingbirds, two groups of birds which are morphologically very specialized, seem to have looked very similar to a small owlet-nightjar, possessing strong legs and a wide gape, while the legs and feet are very reduced in today's swifts and hummingbirds, and the bill is narrow in the latter.
They were thought to have originated in Australasia or Southeast Asia, but the recent discovery of owlet-nightjar fossils in France dating back to the Oligocene suggests otherwise.
- Genus Quipollornis (fossil; Early/Middle Miocene of New South Wales)
- Genus Aegotheles
- New Zealand Owlet-nightjar, Aegotheles
novaezealandiae (prehistoric; formerly Megaegotheles)
New Caledonian Owlet-nightjar, Aegotheles savesi
Feline Owlet-nightjar, Aegotheles insignis
Starry or Spangled Owlet-nightjar, Aegotheles tatei
Moluccan or Long-whiskered Owlet-nightjar, Aegotheles crinifrons
Australian Owlet-nightjar, Aegotheles cristatus
Barred Owlet-nightjar, Aegotheles bennettii
Upland Barred Owlet-nightjar, Aegotheles affinis (formerly A. bennettii affinis
Salvadori's Owlet-nightjar, Aegotheles salvadorii (formerly A. albertisi salvadorii)
Wallace's Owlet-nightjar, Aegotheles wallacii
Archbold's Owlet-nightjar, Aegotheles archboldi
Mountain Owlet-nightjar, Aegotheles albertisi
- New Zealand Owlet-nightjar, Aegotheles novaezealandiae (prehistoric; formerly Megaegotheles)
- Dumbacher, John P. ; Pratt, Thane K. & Fleischer, Robert C. (2003): Phylogeny of the owlet-nightjars (Aves: Aegothelidae) based on mitochondrial DNA sequence. Molecular Phylogenetics and Evolution 29(3): 540–549. DOI:10.1016/S1055-7903(03)00135-0 PDF fulltext
- Mayr, Gerald (2002): Osteological evidence for paraphyly of the avian order Caprimulgiformes (nightjars and allies). Journal für Ornithologie 143: 82–97. PDF fulltext