orange in the male. The sexes are very similar, apart from the crest colour, although the female is a little duller in plumage and on average slightly smaller. Juveniles have a grey tinge to the duller upperparts, and lack the coloured crown; the other head markings are present, but duller than in the adult. By their first winter, only the flight and tail feathers remain unmoulted, and the young birds are virtually indistinguishable from the adults in the field. This kinglet usually hops with its body held horizontally, and its flight is weak and whirring, with occasional quick evasive turns. Adult firecrests are unlikely to be confused with any other species; Pallas's warbler has a similar head and wing pattern, but its crown stripe is pale lemon, not bright yellow or orange, and its supercilium is also pale yellow, not bright white. The juvenile common firecrest might be confused with the goldcrest, but usually shows enough face pattern to distinguish it from its relative, which has a very plain face at all ages. The firecrest can also be separated from Pallas's warbler by the warbler's pale crown stripe and yellow rump. There is more likelihood of confusing the juvenile firecrest with the yellow-browed warbler, which has a similar head pattern; the warbler (an Asiatic species) has pale fringes to the feathers of the closed wing, a whitish belly and darker brown legs. The yellow-browed warbler also lacks the pale half circle present below the young firecrest's eye. Taxonomy and systematics The kinglets are a small group of birds sometimes included in the Old World warblers, but frequently given family status, especially as recent research shows that, despite superficial similarities, the crests are phylogenetically remote from the warblers. The names of the family Regulidae, and the 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 common firecrest was first formally described by Dutch zoologist Coenraad Jacob Temminck in 1820 as Sylvia ignicapilla; the relatively late identification of this common European bird arose from a perception that it was just a variety of the goldcrest. The species name is derived from Latin ignis "fire" and capillus "hair". The binomial is frequently given as R. ignicapillus due to a misunderstanding of Latin grammar. There are two widely recognised subspecies of common firecrest, nominate R. i.