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Nightjars are medium-sized nocturnal or crepuscular in the family Caprimulgidae and order Caprimulgiformes, characterised by long wings, short legs, and very short bills. They are sometimes called bugeaters, their primary source of food being insects. Some New World species are called nighthawks. The English word nightjar originally referred to the European nightjar.
Nightjars are found all around the world, with the exception of Antarctica, and certain island groups such as the Seychelles. They can be found in a variety of habitats, most commonly the open country with some vegetation. They usually nest on the ground, with a habit of resting and roosting on roads.
Nightjars have similar characteristics, including small feet, of little use for walking, and long, pointed wings. Typical nightjars have , longer bills, and softer plumage. The colour of their plumage and their unusual perching habits help conceal them during the day.
The common poorwill, Phalaenoptilus nuttallii, is unique as a bird that undergoes a form of hibernation, becoming torpid and with a much reduced body temperature for weeks or months, although other nightjars can enter a state of torpor for shorter periods.
The cladogram shown below is based on a 2014 phylogenetic study by Snorri Sigurðsson and Joel Cracraft that analysed two mitochondrial and two nuclei loci. The African brown nightjar ( Veles binotatus), was not included in the study. The division of the species into genera is based on version 15.1 of the list of bird species maintained by Frank Gill, Pamela C. Rasmussen and David Donsker on behalf of the International Ornithological Committee. Three non-monophyletic genera are indicated by asterisks. In 2023 Thiago Vernaschi Costa and collaborators proposed that the non-monophyly could be resolved by the introduction of three monotypic genera. They resurrected the genus Antiurus for the spot-tailed nightjar and erected two new genera: Quechuavis for Tschudi's nightjar and Tepuiornis for the Roraiman nightjar.
The family contains 20 genera.
In addition, a fossil species, Ventivorus ragei has been described in 1988 from southwest France by Cécile Mourer-Chauviré based on two partial .
Also see a list of nightjars, sortable by common and binomial names.
A number of species undertake bird migration, although the secretive nature of the family may account for the incomplete understanding of their migratory habits. Species that live in the far north, such as the European nightjar or the common nighthawk, migrate southward with the onset of winter. Geolocators placed on European nightjars in southern England found they wintered in the south of the Democratic Republic of the Congo. Other species make shorter migrations.
They also usually nest on the ground, laying one or two patterned eggs directly onto bare ground. Nightjars possibly move their eggs and chicks from the nesting site in the event of danger by carrying them in their mouths. This suggestion has been repeated many times in ornithology books, but surveys of nightjar research have found very little evidence to support this idea.
Developing conservation strategies for some species presents a particular challenge in that scientists do not have enough data to determine whether or not a species is endangered due to the difficulty in locating, identifying, or categorizing their limited number (e.g. 10,000) known to exist, a good example being the Vaurie's nightjar in China's south-western Xinjiang Province (as seen only once in-hand). Surveys in the 1970s and 1990s failed to find the species, Handbook of the Birds of the World, Volume 5, Birdlife International/Lynx Edicions, 1999 implying that the species has become extinct, endangered, or found only in a few small areas.
Distribution and habitat
Nightjars inhabit all continents other than Antarctica, as well as some island groups such as Madagascar, the Seychelles, New Caledonia and the islands of Caribbean. They are not known to live in extremely arid desert regions. Nightjars can occupy all elevations from sea level to , and a number of species are montane specialists. Nightjars occupy a wide range of habitats, from deserts to rainforests but are most common in open country with some vegetation.
The nighthawks are confined to the New World, and the eared nightjars to Asia and Australia.
Conservation and status
Some species of nightjars are threatened with extinction. Road-kills of this species by cars are thought to be a major cause of mortality for many members of the family because of their habit of resting and roosting on roads.
In history and popular culture
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