The Ruby-crowned Kinglet is a very small passerine bird found throughout North America. It is a member of the Kinglet family. The bird has olive-green plumage with two white wing bars and a white eye-ring. Males have a red crown patch, which is usually concealed. The male and female are identical [apart from the crown], and juveniles are similar in plumage to adults. It is one of the smallest songbirds in North America. The Ruby-crowned Kinglet is not closely related to other kinglets.
The Kinglet is migratory, and its range extends from northwest Canada and Alaska south to Mexico. Its breeding habitat is spruce-fir forests in the northern, mountainous, United States and Canada.
The Ruby-crowned Kinglet builds a cup-shaped nest, which may be pensile or placed on a tree branch and is often hidden. It lays up to 12 eggs, and has the largest clutch of any North American passerine for its size. It is mainly insectivorous, but also eats fruits and seeds.
The Ruby-crowned Kinglet is a very small bird, 12 cm long, having a wingspan of 18 cm, and weighing 10 gm. It has gray-green upperparts and olive-buff underparts. It has two white wingbars and a broken white eye ring. The wingbar on the greater secondary coverts is wider, and is next to a dark band. The kinglet has a relatively plain face and head, although the male has a scarlet-red crown patch, which is usually concealed by the surrounding feathers. The crown patch is rarely orange, yellow, or not present. Females are identical to males [except for the crown]. Immature birds are similar to adult females.
The Kinglet usually moves along branches or through foliage with short hops, and flies with bursts of rapid wing beats. It is constantly active, and is easily recognized by its characteristic wing-flicking.
The bird can be mistaken for the Hutton's Vireo, which also displays wing-flicking, though less frequently than the kinglet. It can also be mistaken for the Dwarf Vireo in Mexico. However, both of the vireos are larger, have stouter bills and legs, and lack the kinglet's black bar on the wings.