"Regulidae" is derived from the Latin word regulus for "petty king" or prince, and refers to the coloured crowns of adult birds.

The long feathers forming the central crown stripe can be erected; they are inconspicuous most of the time, but are used in courtship and territorial displays when the raised crest is very striking.

[1] There are two species of different genera in North America with largely overlapping distributions, and two in Eurasia that also have a considerable shared range.

The two generalists, ruby-crowned kinglet and common firecrest, hunt more in flight and have smoother soles, shorter hind claws and a longer tail.

The exception is the ruby-crowned kinglet, the largest species, which has a strongly red crest and no black crown stripes.

[1][8][9] Kinglets are birds of the Nearctic and Palearctic realms, with representatives in temperate North America, Europe and Asia, northernmost Africa, Macaronesia and the Himalayas.

Kinglets prevented from feeding may lose a third of their body weight in twenty minutes and may starve to death in an hour.

Kinglet nests are small, very neat cups, almost spherical in shape, made of moss and lichen held together with spiderwebs and hung from twigs near the end of a high branch of a conifer.