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The river martins form a distinctive subfamily Pseudochelidoninae within the swallow and martin bird family Hirundinidae. The two species are the African river martin ''Pseudochelidon eurystomina'', found in the Congo and Gabon, and the white-eyed river martin ''Pseudochelidon sirintarae'', known only from one site in Thailand. These are medium-sized, largely black swallows that have a light buoyant flight and feed on insects caught in the air. They appear to be more terrestrial than other swallows, frequently walking rather than perching, and the white-eyed may be crepuscular. The African species excavates nest holes in sandy ridges in rivers, while the breeding locations and habits of the Asian bird are unknown. When the African river martin was first discovered in the 19th century, Gustav Hartlaub thought it was a roller, and later authors either placed it in its own family, or with the woodswallows. Study of the anatomy revealed that the species was closest to the swallows and martins, but that it possessed a number of distinctive features, such as its robust legs and feet and stout bill. These indicated that it should be placed in a separate subfamily. The two river martin species are usually considered to belong to a single genus, ''Pseudochelidon'', due to their having a number of structural similarities. However, Brooke proposed that the white-eyed river martin be placed in a separate monotypic genus ''Eurochelidon''. The African river martin has a restricted distribution; it appears to be locally numerous, although its true status has not been fully investigated. The white-eyed river martin was discovered as recently as 1969 and is only known from specimens and anecdotal evidence – no modern ornithologists have seen the species in the wild, and its breeding grounds are unknown. It may be extinct, although a possible sighting was reported in 2004. ==Taxonomy== When a specimen of the African river martin from Gabon was first formally described by German zoologist Gustav Hartlaub in 1861, it was not initially identified as a member of the swallow and martin family. Hartlaub placed it with the rollers, and later authors either put it in its own separate family, or with the woodswallows. It was only following study of the anatomy of the species by Lowe that it was determined to be closely related to the swallows and martins, but sufficiently different that it could be placed in a separate subfamily Pseudochelidoninae. The genus name ''Pseudochelidon'' comes from the Ancient Greek prefix ''ψευδο/pseudo'', "false", and ''χελιδων''/''chelidôn'', "swallow", reflecting its distinctiveness from the "true" swallows.〔(【引用サイトリンク】url= http://www.xs4all.nl/~sbpoley/scinames.htm )〕 For many years the African river martin was the sole member of its genus and subfamily until the discovery of the white-eyed river martin, ''Pseudochelidon eurystomina'', by Thai ornithologist Kitti Thonglongya in 1968. Although some authorities follow Brooke in placing that species in a separate genus ''Eurochelidon'' due to its significant differences from the African species, it remains a member of the same subfamily. Genetic studies confirmed that the two river martins form a distinct clade from the typical swallows in the Hirundininae subfamily. The river martins are in some ways intermediate between typical swallows and other passerines: they have stout bills, large feet and relatively strong legs, which is unusual in aerial feeders. They also have a large syrinx (vocal organ) and a different bronchial structure. The extent of their differences from other swallows and the wide geographical separation of these two martins suggest that they are relict populations of a group of species that diverged from the main swallow lineage early in its evolutionary history,〔 and they may be the most primitive of the swallows. Like other early hirundine lineages, they nest in burrows, rather than adopted nest holes or mud nests. 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「river martin」の詳細全文を読む スポンサード リンク
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