A kinglet, or crest, is a small bird in a group that is sometimes included in the Old World warblers, but is frequently placed in its own family, Regulidae, because of resemblance to titmice. "Regulidae" is derived from the Latin word regulus for "petty king" or prince, and refers to the colored crowns of adult birds. This family has representatives in North America and Eurasia. There are seven species in this family; one, the Madeira firecrest, Regulus madeirensis, was only recently split from common firecrest as a separate species. One species, the ruby-crowned kinglet, differs sufficiently in its voice and plumage to occasionally be afforded its own genus, Corthylio.