Aegothelidae – Owlet-nightjars

The Aegothelidae or Owlet-nightjars are small crepuscular birds in their own order –  Aegotheliformes. Their closest relatives the Podargiformes (Frogmouths) and Apodiformes (Tree-swifts, Swifts & Hummingbirds). They, however, are an exclusively Australasian group. Most are native to New Guinea, but some species extend to Australia, the Moluccas, and New Caledonia. It is a monotypic family so has just one genus – Aegotheles.

Owlet-nightjars are insectivores that hunt mostly in the air but sometimes on the ground; their soft plumage is a cryptic mixture of browns and paler shades, they have fairly small, weak feet (but larger and stronger than those of frogmouths) and a tiny bill that opens extraordinarily wide, surrounded by prominent whiskers. Their wings are short, with 10 primaries and about 11 secondaries; their tails are long and rounded.

Australian Owlet-nightjar Aegotheles cristatus – Bird-Photo-Tours ASIA

Owlet-nightjars are insectivores that hunt mostly in the air but sometimes on the ground; their soft plumage is a cryptic mixture of browns and paler shades, they have fairly small, weak feet (but larger and stronger than those of frogmouths) and a tiny bill that opens extraordinarily wide, surrounded by prominent whiskers. Their wings are short, with 10 primaries and about 11 secondaries; their tails are long and rounded.

The relationship between the owlet-nightjars and the (traditional) 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. It appears though that that they are not so closely related to either as previously thought, and that the owlet-nightjars share a more recent common ancestor with the Apodiformes. It has been recently been agreed that they should be considered a distinct order, Aegotheliformes. This, the caprimulgiform lineage(s), which has split further into two orders and the Apodiformes, are postulated to form a clade called Cypselomorphae, with the owlet-nightjars and the Apodiformes forming the clade Daedalornithes.

Feline Owlet-nightjar Aegotheles insignis – Bird-Photo-Tours ASIA

A comprehensive 2003 study incorporating DNA sequencing suggests that there are just 9 species of owlet-nightjar; more recently a tenth has been added and they are set out below.

In form and habits, however, they are very similar, at first glance, to small owls with huge eyes. The ancestors of the swifts and hummingbirds, two groups of birds which are morphologically very specialised, 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.

The family Aegothelidae gathers nine species in a single genus (Aegotheles) very similar to Strigidae but also to Caprimulgidae and frogmouths. Depending on the authors, this family is part of the order Apodiformes, following morphological comparative studies.

Another species was native to New Zealand (Aegotheles novaezelandiae), but was been extinct by the early 13th century, predated by Pacific Rats accidentally introduced by the first Māori settlers. It was very large compared to other such species being around 35 cm in length and weighing 150-200 grams, with short wings but with long legs. It may well have been flightless or very nearly so.