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''Delichon'' is a small genus of passerine birds that belongs to the swallow family and contains three species named as house martins. These are chunky, bull-headed and short-tailed birds, blackish-blue above with a contrasting white rump, and with white or grey underparts. They have feathering on the toes and tarsi that is characteristic of this genus. The house martins are closely related to other swallows that build mud nests, particularly the ''Hirundo'' barn swallows. They breed only in Europe, Asia and the mountains of North Africa. Two species, the common and Asian house martins, migrate south in winter, while the Nepal house martin is resident in the Himalayas year-round. The house martins nest in colonies on cliffs or buildings, constructing feather- or grass-lined mud nests. The typical clutch is two or three white eggs; both parents build the nest, incubate the eggs and feed the chicks. These martins are aerial hunters of small insects such as flies and aphids. Despite their flying skills the ''Delichon'' martins are sometimes caught by fast-flying birds of prey. They may carry fleas or internal parasites. None of the species are considered threatened, although widespread reductions in common house martin numbers have been reported from central and northern Europe. This decline is due to factors including poor weather, poisoning by agricultural pesticides, lack of mud for nest building and competition with house sparrows for nest sites. == Taxonomy == The three ''Delichon'' species are members of the swallow family of birds, and are classed as members of the Hirundininae subfamily which comprises all swallows and martins except the very distinctive river martins. DNA studies suggest that there are three major groupings within the Hirundininae, broadly correlating with the type of nest built. The groups are the "core martins" including burrowing species like the sand martin, the "nest-adopters", which are birds like the tree swallow that utilise natural cavities, and the "mud nest builders". The ''Delichon'' species construct a closed mud nest and therefore belong to the latter group; they appear to be intermediate between the ''Hirundo'' and ''Ptyonoprogne'' species that make open cup nests, and the ''Cecropis'' and ''Petrochelidon'' swallows, which have retort-like closed nests with an entrance tunnel. The genetic evidence suggests a close relationship between ''Hirundo'' and ''Delichon'', which is further supported by the frequency of interbreeding between two widespread species, the barn swallow and the common house martin, despite being their being in different genera.〔Turner (1989) p. 9〕 The suggested taxonomic sequence of the mud-building swallows has been recommended by at least two European taxonomic committees. The genus ''Delichon'' was created by American naturalist Thomas Horsfield and British entomologist Frederic Moore in 1854 to accommodate the Nepal house martin that was first described by Moore in the same year, and is therefore the type species for the genus.〔(【引用サイトリンク】work= ) Retrieved 27 December 2009〕 The two other house martins were moved to ''Delichon'' from the genus ''Chelidon'' in which they had been placed up to that time. The name of the new genus, "''Delichon''", is an anagram of the Ancient Greek term χελιδον/''chelidôn'', meaning swallow.〔 Retrieved 27 December 2009〕 The genus contains three similar species:〔Turner (1989) pp. 226–233〕 * Common house martin (''Delichon urbicum'') originally described as ''Hirundo urbica'' by Linnaeus in 1758. * Asian house martin (''Delichon dasypus'') described as ''Chelidon dasypus'' by Bonaparte in 1850.〔Bonaparte's nomenclature is confusing, and he may have intended ''Hirundo dasypus''. See Appendix 1 of 〕 * Nepal house martin (''Delichon nipalense'') described by Moore in 1854.〔 The common and Asian house martins have sometimes been considered to be a single species, although both breed in the western Himalayas without hybridising.〔 There is also limited DNA evidence that suggests a significant genetic distance between these two martins. 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「Delichon」の詳細全文を読む スポンサード リンク
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