Ruby-crowned Kinglets are tiny, active, olive-green to gray songbirds. Their wings are dark, with two white wing-bars. There is a black smudge below the second wing-bar, which is a field mark useful in distinguishing a Ruby-crowned Kinglet from the similar-appearing Hutton’s Vireo. Ruby-crowned Kinglets have bold, incomplete white eye-rings. Their legs are black and their feet, yellow. They are slightly larger than the closely related Golden-crowned Kinglet and lack that species’ black and white head stripes. Male Ruby-crowned Kinglets have bright red crests (that can vary in color to orange), which can be raised when the bird is excited but which are more often completely hidden. Females look like males but lack the red crest.