Golden-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.

There are three migratory subspecies in the United States and Canada, differing in size, bill length, back and rump colours, wing-bar width and colour, and length of supercilium:

• subspecies apache, breeding and wintering from southern Alaska and southern Yukon to southwest California and southern New Mexico. This subspecies is medium-small, has a long bill, and has the back and rump bright yellowish-olive
• subspecies olivaceus, breeding from coastal southeast Alaska to southwest Oregon, wintering to Idaho and southwest California. This subspecis is small, with a medium-long bill, and has the back and rump dark greenish-olive.
• subspecies satrapa, breeding from northern Alberta to Newfoundland and North Carolina. This subspecies is large, with a short bill, has the back and rump olive with a greyish wash. It further differs from apache and olivaceus in two other regards: the white supercilium stops short of the rear of the crown, whereas on the other two species the supercilium extends farther back, and the wingbars are wide, and white (or slightly lemon-tinged) compared with narrow dingy whitish (or lemon- or olive-washed) wingbars of the other two subspecies.

The subspecies "amoenus" has been synonymised with apache as the distinction between these populations are obscured by individual variation.

Two other (non-migratory) subspecies occur south of the bird's core range, although these are weakly differentiated from each other and so are perhaps best synonymised:

• subspecies aztecus in south-central Mexico, in the mountains from Michoacán south to Oaxaca. This subspecies is dark greenish above, has poorly developed wing markings, and its underparts are washed greyish-brown.
• subspecies clarus in the mountains of Chiapas, southern Mexico, and in Guatemala. This subspecies resembles aztecus but is paler and duller, with a shorter tail.

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