Dark-eyed Juncos are between 13 to 17 cm in length. Males are slightly larger and more brightly plumaged than females. While plumage characteristics vary, all Dark-eyed Juncos exhibit a basic plumage form. They are predominately gray above with white or pinkish wash to the undersides, with white outer tail feathers.
Dark-eyed Juncos are flocking birds with a distinct social hierarchy. They forage on the ground in these groups, scratching with their feet to find food. The flash of white tail feathers serve as a signal that alerts members of the flock when one is alarmed.
During the breeding season, Dark-eyed Juncos use a variety of forested habitat, but prefer moist conifer or mixed forests with dense understory and forest openings. During the winter, they can be found in open woodlands and brushy areas including towns, gardens, and shrub-steppe habitat.
Breeds in North America, from north-west Alaska east to Labrador and Newfoundland, south to northern Baja California (Mexico), southern New Mexico, north-west Nebraska, east-central Minnesota, central Michigan, Appalachians south to northern Georgia, and south-east New York. Accidental in Iceland, Britain, Ireland, Netherlands, Denmark, Norway, Sweden, Poland, Gibraltar.
During the summer, about half of the Dark-eyed Junco's diet is made up of insects and other arthropods, the other half consists of seeds. The young eat mostly arthropods. In winter, the diet shifts more to seeds and berries.
This species has a large range, with an estimated global Extent of Occurrence of 10,000,000 km². It has a large global population estimated to be 260,000,000 individuals (Rich et al. 2003). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. [conservation status from birdlife.org]
The male Dark-eyed Junco sings from a high perch to defend his territory and attract a mate. During courtship, both members of a pair hop about on the ground with their wings drooped and their tails spread, showing off their white outer tail feathers. The nest, which the female builds, is almost always on the ground. It is often in a depression, hidden under grass, a log, a rock, or an upturned tree root. The nest is a cup made of grass, moss, lichen, rootlets, twigs, and bark fiber, and is lined with fine grass, hair, or feathers. The female incubates 3 to 5 eggs for 11 to 13 days. Both parents feed the chicks, which leave the nest at 9 to 11 days. Pairs typically raise 1 or 2 broods per year.
Status varies. Northern populations largely migratory. Other populations partially migratory to sedentary according to latitude; some make altitudinal movements. Winters from southern Alaska and southern Canada east to Newfoundland, south throughout USA to northern Mexico. Migration (both seasons) on broad front east of Rockies, with channelling through valleys in west, but movement along coasts is not typical. Frequent vagrant to Canadian and Alaskan Arctic; also recorded north-west to Pribilof islands, and (both seasons) eastern Siberia. Rare vagrant to west Palearctic, especially in spring. 18 records from Britain and Ireland up to 1995, of which 14 in April-May and 4 in December-February; 2 birds present December-March. Individual recorded at Gibraltar 18-25 May 1986 coincided there with arrival of White-throated Sparrow.