Ruby-crowned Kinglet - Taxonomy

Taxonomy

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 Ruby-crowned Kinglet was first described in 1766, in the 12th edition of Carl Linnaeus's Systema Naturae. Its species name means "by the month", and is shared with a genus of flower.

As a result of its larger size, strongly red (rather than orange or yellow) crest and lack of black crown stripes, as well as its distinctive vocalisations, the Ruby-crowned Kinglet is sometimes considered different enough from the Old World kinglets and the other American species, the Golden-crowned Kinglet, to be sometimes assigned to a separate genus, Corthylio.

Up to five subspecies have been recognized, but "cineraceus", breeding in montane western North America, and "arizonensis", breeding in Arizona, are considered to be clinal variants of the nominate subspecies. The form grinnellii, breeding from southeast Alaska to British Columbia differs significantly from nominate calendula, and so is considered to be represent a valid subspecies: it is smaller and shorter-winged, its upperparts are darker and greener, its underparts are buffy rather than grayish olive, and the vent is tinged yellow rather than dull whitish olive. The subspecies obscurus, from Guadalupe Island, off Baja California, is considered endangered, and may already be extinct.

Hybridization with Golden-crowned Kinglet has been reported to have possibly occurred.