An extremely small (4 inches) songbird, the male Ruby-crowned Kinglet is most easily identified by its small size, olive-green body, white eye-rings, black wings with white wing bars, and solid red crown. Female Ruby-crowned Kinglets are similar, but lack the male’s red crown. Both sexes may be separated from the related Golden-crowned Kinglet (Regulus satrapa) by that species’ pale face, black eye-stripe, and yellow on the head. The Ruby-crowned Kinglet breeds across Alaska, Canada, and the northern tier of the United States. In the west, this species’ range extends south at higher elevations as far as southern Arizona. In winter, most populations migrate south to the southern half of the U.S., along the Pacific coast from British Columbia to California, and in Mexico, although some populations breeding in the mountain west simply winter at lower altitudes nearby. Ruby-crowned Kinglets breed in northern and high-mountain evergreen forests. In winter, this species may be found in a variety of forest habitats from temperate deciduous woodland to open tropical forest. Ruby-crowned Kinglets primarily eat small insects and spiders, but will also eat fruit and seeds during the winter or when invertebrates are not available. In appropriate habitat, Ruby-crowned Kinglets may be observed flitting through the forest canopy while plucking small invertebrates from leaves or evergreen needles. Birdwatchers may also listen for this species’ song, a series of high chirps followed by a jumble of notes and a trill. Ruby-crowned Kinglets are primarily active during the day.