Dark-eyed juncos are unique sparrows that nest on or near the ground in forests. In winter, they typically form flocks and often associate with other species, including chipping sparrows, pine and palm warblers (in the southeastern United States.), and bluebirds. When disturbed the entire flock suddenly flies up to a tree, usually perching in the open and calling in aggravation at the intrusion. Polytypic. Length 6.3".
A fairly lean sparrow with a long notched tail and a small pinkish or horn-colored bill (bicolored in dorsalis). Two prominent white outer tail feathers in most subspecies; 3 outermost in the “white-winged.” Most subspecies have a gray or brown head and breast sharply set off from a white belly. Otherwise highly variable. Male: typically darker with sharper markings. Female: typically browner with more indistinct markings. Juvenile: heavily streaked, often with a trace of adult pattern.
The 12 subspecies show marked variation and fall into 5 major groups: “white-winged” (1 ssp.), “Slate-colored” (2 subtle ssp., plus cismontanus), “Oregon” (5 subtle ssp.), “pink-sided” (1 ssp.), and “gray-headed” (2 distinctive ssp.). The groups have at times been considered separate species. The “white-winged” junco is the most local, breeding exclusively in the Black Hills region and wintering along the eastern edge of the Rockies; it is casual to accidental in western Texas, Arizona, and southern California. The “slate-colored” is the most widespread and the only form found regularly in the East. It breeds throughout the species’ range east of the Rockies and in the northern region; it winters mainly in the East and is uncommon to rare in the West. The “Oregon” junco breeds in the West Coast states north to southern Alaska and east to central Nevada and western Montana; it winters throughout the West and Great Plains and is casual to the East. The “pink-sided” breeds in the northern Rockies, centered on Yellowstone and ranging from northern Utah to southernmost Alberta and Saskatchewan; it winters in the southern Rockies, Southwest, and western Great Plains, rarely to the West Coast, and is accidental to the East. The “gray-headed” is the subspecies of the southern Rockies, breeding through much of Nevada, Utah, and Colorado south to central Arizona and western Texas; it winters in the southwest and southern Rockies states and is rare to the West Coast and accidental to the East.
The distinctive “white-winged junco,” aikeni, is mostly pale gray above, usually with 2 thin white wing bars; it is also larger, with more white on its tail. It is most similar to the “Slate-colored” (which can rarely have narrow wingbars) but is larger and paler, with contrasting blackish lores and more extensive white in the tail. The male “slate-colored junco” has a white belly contrasting sharply with a dark gray hood and upperparts, usually with very little contrast between the hood and back; immatures can have some brown wash on the back and crown. In the female, the amount of brown on the head and at the center of the back varies; it’s more extensive in immatures. The “slate-colored junco” comprises 2 subspecies: the widespread nominate and the larger, bluer-billed carolinensis, which is resident in the Appalachians from Pennsylvania to northern Georgia. An additional subspecies, cismontanus, is often grouped with the “slate-colored.” It breeds from the Yukon to central British Columbia and Alberta and may winter throughout the West; it is casual to the East. Cismontanus is intermediate between the “slate-colored” and the “Oregon,” with males showing a blackish hood that contrasts with a usually grayish back (occasionally with some brown). Females and immatures are very similar to the “Oregon” juncos, but are less distinctly hooded. The male “Oregon” junco has a slaty to blackish hood, contrasting sharply with its rufous-brown to buffy-brown back and sides; the female has duller hood color. Of the 5 “Oregon” subspecies, the more southerly subspecies are paler. The “pink-sided” junco, mearnsi, has broad, bright pinkish cinnamon sides, a blue-gray hood, a poorly defined reddish brown back and wings that do not contrast markedly with the flanks, and blackish lores. Females duller, but retain basic pattern; they can resemble “Oregon” females closely. In the “gray-headed” junco, the pale gray head and dark lores resemble the head pattern of the “pink-sided,” but the flanks are gray rather than pinkish, and the back is marked by a very well-defined patch of reddish hue that does not extend to the wings and that contrasts sharply with the rest of the body. A distinctive subspecies, dorsalis, is sometimes known as the “red-backed” junco and is resident from northwestern Arizona through New Mexico to the Guadalupe Mountains of western Texas. It differs from the more widespread, migratory, northerly breeding caniceps in having an even paler throat and a larger, bicolored bill that is black above and bluish below. Intergrades between some subspecies are frequent. Common intergrades are: “pink-sided” x “oregon” and “pink-sided” x “gray-headed.” Cismontanus may be a broad intergrade population of “Oregon” x “slate-colored” juncos. Identification to subspecies group thus requires caution to eliminate the possibility of an intergrade; for intergrades, look for intermediate characteristics: For example, a darker, more contrasting hood on a “pink-sided” indicates the influence of “Oregon” genes; reduced pink sides and a well-defined reddish back on a “pink-sided” indicate “gray-headed” parentage.
Songs and calls among the subspecies are generally similar, but songs and calls of the “gray-headed” dorsalis are more suggestive of the yellow-eyed junco. Call: sharp dit. Flight note: a rapid twittering. Song: a musical trill on 1 pitch; often heard in winter.
Status and Distribution
Common. Breeds south to northern Baja California; winters south to northern Mexico. Breeding: breeds in coniferous or mixed woodlands. Winter: found in a wide variety of habitats, the dark-eyed junco tends to avoid areas of denser brush; it especially favors feeders, parks, and open forest without an understory. Migration: withdraws from wintering areas during April, typically early–mid-April. Fall arrivals first appear in late September, peaking in late October. Vagrant: southern Florida and Europe.
—From the National Geographic book Complete Birds of North America, 2006