The Australian owlet-nightjar (Aegotheles cristatus) is a nocturnal bird found in open woodland across Australia and in southern New Guinea. It is the smallest nocturnal bird found in Australia, making it prone to predation. It is colloquially known as the moth owl or fairy owl and Jarlajirrpi by the Warlpiri people. It is the most common nocturnal bird in Australia. Despite suffering from predation and competition by introduced species, it is not considered threatened. The species was described in the same year by John Latham as Caprimulgus novaehollandiae but Shaw's account is believed to be earlier and thus has precedence. The Australian owlet-nightjar was previously placed in Caprimulgiformes but updated taxonomy now places it in Aegotheliformes. The Australian owlet-nightjar is now one of ten species placed in the genus Aegotheles that was introduced in 1827 by the naturalists Nicholas Vigors and Thomas Horsfield. It is the type species of the genus. The specific epithet cristatus is Latin meaning "crested", "plumed" or "tufted".
Two subspecies are recognised: making it a small to medium-sized owlet-nightjar with grey upperparts and a white, barred front and a distinct dark and pale patterning on the head. It has large dark eyes that are non-reflective when a light is shone upon them; unlike many other nocturnal birds. Juvenile birds are similar to adults with slightly more spotting, shorter face bristles, and blurred markings on the face and nape. To combat lower temperatures in winter, Australian owlet-nightjars increase feather insulation to keep warm. This relies on panting and gular fluttering. Being a nocturnal species, Australian owlet-nightjars are reluctant to leave roost sites during the day, and cannot seek out water to rehydrate that lost from panting. They usually enter torpor once a day around dawn for 3–4 hours, if they enter torpor twice in a day it is always a morning bout followed by a bout in the afternoon or night. Australian owlet-nightjars enter torpor more during periods of low arthropod abundance, likely to conserve energy and reduce the need for food.
Habitat and distribution
Australian-owlet nightjars are widespread in Australia and are a hollow-dependent species, meaning they use tree hollows for both roosting and nesting. In Australia they can be found in suburban and urban-fringe environments. In New Guinea this species is commonly found in savannah, while in Australia it has a preference for open mature woodland and habitats containing eucalyptus and acacia. On average they move between roost sites over a distance of about 300m every 9 days and in one study used between 2-6 different cavities over a 6 month period. These gates are used to restrict access to private and crown land and when opened occasionally flush Australian owlet-nightjars that were roosting inside. They have also been found roosting in roof cavities and chimneys. Australian owlet-nightjars that hunt on moonlit nights face a trade-off, as they hunt using vision but are also at a greater risk from predation by other visual hunters (e.g. owls).
Reproduction
The Australian owlet-nightjar nests mainly in holes in trees (or in other holes and crevices), which is provisioned with leaves by both of the pair. It is thought that the frequent addition of eucalyptus leaves is because they act as a beneficial insecticide. Australian owlet-nightjar pairs are thought to mate for life, and pairs breed between August and December. Three or four eggs are laid, and incubated by the female for just under a month. Both the adults feed the chicks, which fledge after a month. The young birds are reported to stay close to the parents for several months after they fledge.
Relationship with humans
Australian owlet-nightjars have an important cultural significance to the Warlpiri people; it is thought of as connected to the Kurdaitcha man, a ritual executioner. The Australian owlet-nightjars is called Jarlajirrpi and its call is said to warn of the approach of the Kurdaitcha.