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Nightjars are medium-sized nocturnal or crepuscular birds in the family Caprimulgidae, characterized by long wings, short legs and very short bills. They are sometimes called goatsuckers, due to the ancient folk tale that they sucked the milk from goats (the Latin for goatsucker is ''Caprimulgus''). Some New World species are called nighthawks. Nightjars usually nest on the ground. The English word 'nightjar' originally referred to the European nightjar. Nightjars are found around the world. They are mostly active in the late evening and early morning or at night, and feed predominantly on moths and other large flying insects. Most have small feet, of little use for walking, and long pointed wings. Their soft plumage is cryptically coloured to resemble bark or leaves. Some species, unusual for birds, perch along a branch, rather than across it. This helps to conceal them during the day. Bracken is their preferred habitat. 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. Nightjars lay one or two patterned eggs directly onto bare ground. It has been suggested that nightjars will 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 while this may accidentally happen, surveys of nightjar research have found very little evidence to support this idea. == Conservation challenge == Working out conservation strategies for some species of nightjar presents a particular challenge common to other hard-to-see families of birds; in a few cases, humans do not have enough data on whether a bird is rare or not. This has nothing to do with any lack of effort. It reflects, rather, the difficulty in locating and identifying a small number of those species of birds among the 10,000 or so that exist in the world, given the limitations of human beings. A perfect example is the Vaurie's nightjar in China's south-western Xinjiang. It has been seen for certain only once, in 1929, a specimen that was held in the hand. Surveys in the 1970s and 1990s failed to find it.〔''Handbook of the Birds of the World'', Volume 5, Birdlife International/Lynx Edicions, 1999〕 It is perfectly possible that it has evolved as a species that can really be identified in the wild only by other Vaurie's nightjars, rather than by humans. As a result, scientists do not know whether it is extinct, endangered, or even locally common. 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「Nightjar」の詳細全文を読む スポンサード リンク
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