|Species:|| Regulus satrapa|
Adults are olive-gray on the upperparts with white underparts, with thin bills and short tails. They have white wing bars, a black stripe through the eyes and a yellow crown surrounded by black. The adult male has an orange patch in the middle of the yellow crown. The juvenile is similar to the adult, but with a browner back and without the yellow crown. This is one of the smallest passerines in North America. Its length, at 8 to 11 cm (3.1 to 4.3 in), is probably the shortest of any American passerine. However, its weight, which averages around 5.9 g (0.21 oz), with a range of 4 to 7.8 g (0.14 to 0.28 oz), is marginally more on average than the long-tailed bushtit and black-tailed gnatcatcher.
These tiny songbirds usually stay concealed high in dense trees, revealing their presence with thin, very high-pitched calls. They pluck small insects from clusters of conifer needles, often hovering briefly to reach them. In migration and winter, kinglets frequently join other insectivorous songbirds such as warblers in mixed flocks.