 The kinglets are a small group of birds sometimes included in the Old World warblers, but frequently given family status, especially as recent research showed that, despite superficial similarities, the crests are taxonomically remote from the warblers. The names of the family, Regulidae, and its only genus, Regulus, are derived from the Latin regulus, a diminutive of rex, "a king", and refer to the characteristic orange or yellow crests of adult kinglets. The species name madeirensis is derived from the island on which this bird is found. The Madeira firecrest was first described by English naturalist Edward Vernon Harcourt in 1851. Until recently, it was considered to be a subspecies, R. i. madeirensis, of the common firecrest R. ignicapillus. A phylogenetic analysis based on the cytochrome b gene showed that the Madeiran form is distinct at the species level from the firecrest nominate subspecies R. i. ignicapillus. Cytochrome b gene divergence between the Madeira firecrest and the European bird is 8.5 %, comparable with the divergence level between other recognised Regulus species, such as the 9 % between the goldcrest and the golden-crowned kinglet. The split was accepted by the Association of European Rarities Committees (AERC) in 2003, but some authorities, such as Clements, have not yet recognised the new species. The International Ornithological Congress' recommended English name for this species was "Madeiracrest", but this has been changed to "Madeira firecrest".
