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The Caprimulgiformes is an order of birds that includes a number of birds with global distribution (except Antarctica). They are generally insectivorous and nocturnal. The order gets its name from the Latin for "goat-milker", an old name based on an erroneous view of the European nightjar's feeding habits. == Systematics == The classification of the various birds that make up the order has long been controversial and difficult, particularly in the case of the nightjars. All things considered, the nightjar order would probably best be limited to potoos, nightjars, and eared-nightjars, all other lineages being elevated to order level, and the owlet-nightjars being altogether distant: * Family Steatornithidae (oilbird) – probably distinct order N.N. ("Steatornithiformes"〔Apparently not a valid taxon (yet), and thus it must not be written without quotation marks.〕) * Family Podargidae (frogmouths, 15 species in 3 genera) – probably distinct order Podargiformes * Family Nyctibiidae (potoos, about 5 species in 1 genus) * Family Caprimulgidae * * Subfamily Chordeilinae (New World nighthawks) * * Subfamily Caprimulginae (typical nightjars) * Family Eurostopodidae (eared nightjars) Traditionally, they were regarded, on morphological grounds, as being midway between the owls (Strigiformes) and the swifts. Like the owls, they are nocturnal hunters with a highly developed sense of sight, and like the swifts they are excellent flyers with small, weak legs. At one time or another, they have been allied with owls, swifts, kingfishers, hoopoes, mousebirds, hornbills, rollers, bee-eaters, woodpeckers, trogons and hummingbirds. Based on analysis of DNA sequence data – notably β-fibrinogen intron 7 – Fain and Houde considered the families of the Caprimulgiformes to be members of the proposed clade Metaves, which also includes the hoatzin, tropicbirds, sandgrouse, pigeons, kagu, sunbittern, mesites, flamingos, grebes and swifts and hummingbirds.〔 This clade was also found by the expanded study of Ericson ''et al.'' (2006), but support was extremely weak.〔 While only the latter study recovered monophyly of the Cypselomorphae (see below) within Metaves, the former was based on only a single locus and could not resolve their relationships according to standard criteria of statistical confidence. No morphological synapomorphies have been found that uniquely unite Metaves (or Caprimulgiformes for that matter), but numerous unlinked nuclear genes independently support their monophyly either in majority or whole. Ericson ''et al.'' (2006) concluded that if valid, the "Metaves" must originate quite some time before the Paleogene, and they reconciled this with the fossil record.〔 While the relationships of cypselomorphs are a subject of ongoing debate, the phylogeny of the individual lineages is better resolved. Much of the remaining uncertainty regards minor details. Initial mtDNA cytochrome ''b'' sequence analysis〔 agreed with earlier morphological〔 and DNA-DNA hybridization〔 studies insofar as that the oilbird and the frogmouths seemed rather distinct. The other lineages appeared to form a clade, but this is now known to have been caused by methodological limitiations. The Aegothelidae (owlet-nightjars) with about a dozen living species in one genus are apparently closer to the Apodiformes; these and the Caprimulgiformes are closely related, being grouped together as Cypselomorphae. The oilbird and the frogmouths seem quite distinct among the remaining Caprimulgiformes, but their exact placement cannot be resolved based on osteological data alone.〔 Even the study of Ericson ''et al.'' could not properly resolve the oilbird's and frogmouths' relationships beyond the fact that they are quite certainly well distinct. It robustly supported, however, the idea that the owlet-nightjars should be considered closer to Caprimulgiformes, unlike the methodologically weaker studies of Mariaux & Braun (1996)〔 and Fain and Houde (2004).〔 Alternatively, Mayr's phylogenetic taxon Cypselomorphae might be placed at order rank and substitute the two present orders Caprimulgiformes and Apodiformes. Such a group would be fairly uninformative as regards its evolutionary history, as it has to include some very plesiomorphic and some extremely derived lineages (such as hummingbirds) to achieve monophyly.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Caprimulgiformes」の詳細全文を読む スポンサード リンク
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