Dark-eyed juncos (Junco hyemalis) breed from Alaska and central Yukon to Labrador and Newfoundland, south to central coastal California, in the mountains to eastern California, central Arizona, and western Texas, southern Alberta, northern and east-central Minnesota, central Michigan, southern New England, and in the Appalachian Mountains to northern Georgia and northwestern South Carolina; also in the Black Hills. This species winters from central and south coastal Alaska, coastal British Columbia and across southern Canada south to Mexico, the Gulf Coast and northern Florida. It is found only in the Nearctic region of the world.
Biogeographic Regions: nearctic (Native )
Because it inhabits open areas, Junco hyemalis is subject to attack by many different birds, including sharp-shinned hawks, shrikes and owls. They are also frequently killed by feral and domestic cats. Red squirrels (Tamiasciurus hudsonicus), weasels (genus Mustela), chipmunks (genus Tamias), American martens (Martes americana) and other mammals as small as jumping mice take eggs and young from nests.
In response to predators, adults flee to nearby shelter. Parents give "chips" excitedly and fly around nest areas when predators are present and sometimes even dive at predators attempting to prey on nestlings or eggs.
Known Predators:
All J. hyemalis are small and slender with an overall length of 5 to 6.5 inches (12.5 to 16.5 cm). This species has dark gray plumage on its head, breast and upper parts which are a contrast to their striking white, outer tail and white belly. Sexes are colored or patterned differently with female and immature J. hyemalis somewhat browner than the adult male; juveniles also have streaked breasts. Males are usually around 5% larger than females. Members of this species have a pink bill and dark eyes. A typical weight for J. hyemalis is 0.67 oz (19 g) and an average wingspan is 9.25 inches (23.5 cm).
Average mass: 19 g.
Range length: 12.5 to 16.5 cm.
Average wingspan: 23.5 cm.
Average basal metabolic rate: 46 cm3.O2/g/hr.
Other Physical Features: endothermic ; bilateral symmetry ; polymorphic
Sexual Dimorphism: male larger; sexes colored or patterned differently
Average mass: 18 g.
Average basal metabolic rate: 0.2959 W.
The average lifespan of J. hyemalis is approximately 3 to 11 years. The oldest known wild dark-eyed junco lived at least 11 years 1 month. Most commonly, predation by other species (hawks, squirrels, weasels, etc.) limits their lifespan.
Range lifespan
Status: wild: 11.1 (high) years.
Typical lifespan
Status: wild: 3 to 11 years.
The habitat of J. hyemalis occurs from sea level to timberline in a variety of woodland areas that have openings with dense herbaceous ground cover. These areas include coniferous and deciduous forests, forest edges, woodland clearings, stream borders, open woodlands, brushy cover bordering mountain meadows, and old barns. This species avoids deep forest interiors in favor of woodland edges and openings. In winter they prefer weedy fields, but also inhabit open woodlands, hedgerows, suburbs, and farmyards. They are found from sea level to 3500 meters.
Range elevation: 0 to 3500 m.
Habitat Regions: temperate ; polar ; terrestrial
Terrestrial Biomes: forest
Other Habitat Features: urban ; suburban ; agricultural ; riparian
Dark-eyed juncos forage on the ground, picking up a wide variety of seeds and some insects. In the non-breeding season, they prefer to feed on insects, non-insect arthropods, and seeds. During the breeding season, they eat mostly insects. They are commonly seen at bird feeders during migration and in the winter months, however, even then they prefer to feed on the ground rather than pick seeds from an elevated feeder. One method of foraging practiced by this species is "riding" a grass stem. This is accomplished by flying up onto a tall grass stem, riding the stem down to the ground as it bends under the bird's weight, and then plucking the seeds from the seed head as it sits on the ground. When a thin layer of snow lies on the ground, dark-eyed juncos scratch away a roughly circular hole, 3 or 4 inches in diameter, to get at the grain underneath. In the summer, half of the diet consists of insects. Caterpillars, beetles, and ants are the most common items in their diet. There is also a long list of mostly weed plants whose seeds J. hyemalis is known to eat. The most common are ragweed, bristlegrass, dropseed grass, crabgrass, pigweed, and goosefoot. Juncos are morphologically generalized enough to handle both seeds and insects as part of their diet.
Animal Foods: insects; terrestrial non-insect arthropods
Plant Foods: seeds, grains, and nuts
Primary Diet: omnivore
Dark-eyed juncos, like many other bird species, are an integral part of forested ecosystems and play an important role in maintaining the health and productivity of the forests and woodlands. Members of this species aid in the dispersal of seeds and help to control insect populations. They are occasionally parasitized by brown-headed cowbirds (Molothrus ater). Antibodies of the St. Louis strain of encephalitis have been reported in dark-eyed juncos and there are 26 other genera of parasites that have been reported to use this species as a host.
Ecosystem Impact: disperses seeds
Junco hyemalis has little, if any, economic importance for humans. This species is an excellent subject for photography and art and provides an enjoyable pastime for many bird watchers. Due to the fact that they are commonly found at bird feeders during migration and winter months, they may play a small part in the sale and production of bird seed, bird feeders and binoculars. Juncos also eat insects that humans may consider pests.
Positive Impacts: controls pest population
There are no known adverse affects of dark-eyed juncos on humans.
Dark-eyed juncos are protected under the US Migratory Bird Treaty Act. They are quite abundant within their geographic range.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Dark-eyed juncos (Junco hyemalis) possess considerable variation in song. The most common song is a simple, musical trill, all in one pitch, or a series of rapid notes which may be too rapid to discern. Only male dark-eyed juncos sing. To proclaim occupancy of a territory, two or three trills on different pitches may be joined to form a single warbling song. A simple explosive call is used as an alarm, while a smacking sequence is used to scold. This species uses a combination of twanging, buzzing, and smacking notes when fighting.
Junco hyemalis also uses territorial and courtship displays to communicate (see Mating Systems and Behavior).
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
There are several distinctive races or groups of races of Junco hyemalis that were formerly considered to be separate species. However, because they interbreed freely where their ranges overlap, they are now treated as a single species. The common names of these former species are still used to refer to these identifiable forms of J. hyemalis. Included in this group are the "Dark-eyed" Junco, the "Slate-colored" Junco, the "White-winged" Junco, Oregon Junco, and the "Gray-headed" Junco. These sub-species were considered separate species until the 1970's when their rank was lowered from species to sub-species.
Dark-eyed juncos are monogamous. Males usually arrive on breeding grounds in the spring, well in advance of the start of nesting, and pairs are formed by mid-April. Males claim territories by singing from the top of the tallest trees in a 2 to 3 acre area. When a female enters his territory, the male pursues her aggressively. He spreads his tail and struts around the female, uttering "chips" and songs. The male may alternate dropping his tail to the ground with lifting it at a 45 degree angle. Once a pair is formed, males follow their mates and are seldom more than 50 feet away. The only exception is when the male proclaims his occupancy of a territory from a high perch.
Mating System: monogamous
The breeding season for dark-eyed juncos begins in April. Females build the nest over a period of 1 to 9 days, but the male often helps by bringing nest material. Nests are commonly built on the ground near the edge of openings in wooded areas or in a slight depression. They are usually well concealed under weeds, grasses, fallen logs, tree roots, or other overhead shelter. Nests are occasionally built up to 8 feet above ground in a shrub or tree. The nest cup is often lined with fine grasses, mosses or mammal hair and is used for two or three broods in one season.
The female lays 3 to 6 white or pale green eggs spotted with brown. The eggs are usually ovate and slightly glossy. Average egg size is about 0.8 inches (19 mm). The incubation period lasts 12 to 13 days; incubation is usually done by the females. Chicks leave the nest 9 to 13 days after hatching. After leaving the nest, the young remain at least partially dependent on their parents for about 3 weeks. Most dark-eyed juncos begin breeding at at 1 year.
Breeding interval: May breed 2 to 3 times during the spring and early summer each year
Breeding season: Dark-eyed juncos begin breeding in April
Range eggs per season: 3 to 6.
Average eggs per season: 4.
Average time to hatching: 12 to 13 days.
Range fledging age: 9 to 13 days.
Range time to independence: 9 to 21 days.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; oviparous
Average time to hatching: 11 days.
Average eggs per season: 4.
The female parent incubates the eggs and broods the chicks after they hatch. Both parents defend the nest from predators, remove fecal sacs from the nest and feed the chicks regurgitated or partly digested food along with an occasional tender caterpillar. Chicks are altricial and begin to open their eggs at the end of the second day. Their feathers begin to show around the seventh day. Rapid tarsal development enables nestlings to run from the nest if threatened before they can fly. Youngsters leave the nest 9 to 13 days after hatching. After leaving the nest, the young remain at least partially dependent on their parents for food for about 3 weeks. Occasionally, young will attempt to solicit parental care and crouch in a begging posture even after they are adequately developed for independence. Parents become aggressive in these cases and chase the fledgling a short distance without feeding it.
Parental Investment: no parental involvement; altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female)
A medium-sized (5 ½ - 6 ¾ inches) bunting, the Dark-eyed Junco comprises several geographic races possessing different patterns of plumage coloration. The eastern “Slate-colored Junco” is slate gray above and white below. The northwestern “Oregon Junco” is black on the head and breast with a chestnut back, gray wings, and white belly. The southern Rocky Mountains “Gray-headed Junco” is light gray on the head, breast, and tail with a chestnut back. The western Plains “White-winged Junco” is similar to the eastern race, but has strong white wing bars. Another race, the northern Rocky Mountains “Pink-sided Junco” is similar to the northwestern race, but is lighter gray on the head, wings, and tail. These races interbreed where their ranges overlap, producing hybrid birds with intermediate plumage. All races of this “snowbird” have in common a pale bill, dark eyes, and white feathers on the outer tail. Female Juncos are similar to males in the same race, but are usually paler and duller. The Dark-eyed Junco breeds across much of Alaska, Canada, and the northern United States, extending southwards at higher elevations to northern Georgia in the east and to Texas in the west. Dark-eyed Juncos are present all year in southern portions of this species’ breeding range, but birds breeding in these areas are displaced southward by more northern birds during winter, when this species may be found across southern Canada, the U.S., and northern Mexico. Dark-eyed Juncos breed in a variety of habitats across this species’ extensive breeding range, all of which have in common cool summer temperatures and some form of forest cover. During the winter, this species inhabits forest edges and other semi-open habitats, and will often enter urban or suburban areas where food is plentiful. Dark-eyed Juncos eat a variety of seeds and other plant material, but will also eat insects when available. In appropriate habitat, Dark-eyed Juncos may be most easily seen foraging for food on the ground or in the branches of trees. In winter, this species may be seen foraging as part of large flocks containing multiple species of sparrows and buntings. Dark-eyed Juncos are most active during the day, but, like many migratory songbirds, this species migrates at night.
A medium-sized (5 ½ - 6 ¾ inches) bunting, the Dark-eyed Junco comprises several geographic races possessing different patterns of plumage coloration. The eastern “Slate-colored Junco” is slate gray above and white below. The northwestern “Oregon Junco” is black on the head and breast with a chestnut back, gray wings, and white belly. The southern Rocky Mountains “Gray-headed Junco” is light gray on the head, breast, and tail with a chestnut back. The western Plains “White-winged Junco” is similar to the eastern race, but has strong white wing bars. Another race, the northern Rocky Mountains “Pink-sided Junco” is similar to the northwestern race, but is lighter gray on the head, wings, and tail. These races interbreed where their ranges overlap, producing hybrid birds with intermediate plumage. All races of this “snowbird” have in common a pale bill, dark eyes, and white feathers on the outer tail. Female Juncos are similar to males in the same race, but are usually paler and duller. The Dark-eyed Junco breeds across much of Alaska, Canada, and the northern United States, extending southwards at higher elevations to northern Georgia in the east and to Texas in the west. Dark-eyed Juncos are present all year in southern portions of this species’ breeding range, but birds breeding in these areas are displaced southward by more northern birds during winter, when this species may be found across southern Canada, the U.S., and northern Mexico. Dark-eyed Juncos breed in a variety of habitats across this species’ extensive breeding range, all of which have in common cool summer temperatures and some form of forest cover. During the winter, this species inhabits forest edges and other semi-open habitats, and will often enter urban or suburban areas where food is plentiful. Dark-eyed Juncos eat a variety of seeds and other plant material, but will also eat insects when available. In appropriate habitat, Dark-eyed Juncos may be most easily seen foraging for food on the ground or in the branches of trees. In winter, this species may be seen foraging as part of large flocks containing multiple species of sparrows and buntings. Dark-eyed Juncos are most active during the day, but, like many migratory songbirds, this species migrates at night.
The dark-eyed junco (Junco hyemalis) is a species of junco, a group of small, grayish New World sparrows. This bird is common across much of temperate North America and in summer ranges far into the Arctic. It is a very variable species, much like the related fox sparrow (Passerella iliaca), and its systematics are still not completely untangled.
The dark-eyed junco was formally described by the Swedish naturalist Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae as Fringilla hyemalis. The description consisted merely of the laconic remark "F[ringilla] nigra, ventre albo. ("A black 'finch' with white belly") and a statement that it came from America.[2] Linnaeus based his description on the "Snow-Bird" that Mark Catesby had described and illustrated in his The Natural History of Carolina, Florida and the Bahama Islands.[3]
The Bill of this Bird is white: The Breast and Belly white. All the rest of the Body black; but in some places dusky, inclining to Lead-color. In Virginia and Carolina they appear only in Winter: and in Snow they appear most. In Summer none are seen. Whether they retire and breed in the North (which is most probable) or where they go, when they leave these Countries in Spring, is to me unknown. [italics in original][3]
The type locality was restricted to South Carolina by the American Ornithologists' Union in 1931.[4][5] The dark-eyed junco is now placed in the genus Junco that was introduced in 1831 by the German naturalist Johann Georg Wagler.[6][7] The genus name Junco is the Spanish word for rush, from the Latin word juncus.[8] Its modern scientific name means "winter junco", from the Latin word hyemalis "of the winter".[9]
Either 14 or 15 subspecies are recognised[7] which are grouped in two or three large or polytypic groups and three or four small or monotypic ones, all depending on the authority. These groups were formerly considered separate species, but they interbreed extensively in areas of contact. Birders trying to identify subspecies are advised to consult detailed identification references.[10][11]
These two or three subspecies have dark slate-gray heads, breasts and upperparts. Females are brownish-gray, sometimes with reddish-brown flanks.[10] They breed in the North American boreal forests from Alaska to Newfoundland and south to the Appalachian Mountains, wintering throughout most of the United States. They are relatively common across their range.
This subspecies has a medium-gray head, breast, and upperparts with white wing bars. Females are washed brownish. It has more white in the tail than the other 14 subspecies. It is a common endemic breeder in the Black Hills of South Dakota, Wyoming, Nebraska, and Montana, and winters south to northeastern New Mexico.[12][10]
These eight subspecies have blackish-gray heads and breasts with brown backs and wings and reddish flanks, tending toward duller and paler plumage in the inland and southern parts of its range.[11] Oregon dark-eyed juncos are also less commonly known as brown-backed dark-eyed juncos. This is the most common subspecies group in the West, breeding in the Pacific Coast Ranges from southeastern Alaska to extreme northern Baja California and wintering to the Great Plains and northern Sonora. An unresolved debate exists as to whether this large and distinct subspecies group is actually a separate species with eight (or nine, see below) subspecies of its own.
Sometimes considered a ninth subspecies in the Oregon/brown-backed group, this subspecies has a lighter gray head and breast than the eight Oregon/brown-backed dark-eyed juncos, with contrasting dark lores. The back and wings are brown. It has a pinkish-cinnamon color that is richer and covers more of the flanks and breast than in the eight Oregon/brown-backed dark-eyed juncos. It breeds in the northern Rocky Mountains from southern Alberta to eastern Idaho and western Wyoming and winters in central Idaho and nearby Montana and from southwestern South Dakota, southern Wyoming, and northern Utah to northern Sonora and Chihuahua.[11]
This subspecies is essentially rather light gray on top with a rusty back. It breeds in the southern Rocky Mountains from Colorado to central Arizona and New Mexico, and winters into northern Mexico.[12][10]
Sometimes included with the gray-headed dark-eyed junco proper as part of the gray-headed group, this subspecies differs from it in having a more silvery bill[11] with a dark-colored upper mandible and light-colored lower mandible,[12][10] a variable amount of rust on the wings, and pale underparts. This makes it similar to the yellow-eyed junco (Junco phaeonotus), except for the dark eyes. It is found in the southern mountains of Arizona and New Mexico.[10] It does not overlap with the yellow-eyed junco in its breeding range.
The extremely rare Guadalupe junco (Junco insularis) was formerly considered to be a subspecies of this species (either included in the gray-headed group or placed in a seventh group of its own, the Guadalupe group), but is now treated as a separate species in its own right – perhaps a rather young one, but certainly this population has evolved more rapidly than the 14 or 15 subspecies of the dark-eyed junco on the mainland due to its small population size and the founder effect.[7]
Adult dark-eyed juncos generally have gray heads, necks, and breasts, gray or brown backs and wings, and a white belly, but show a confusing amount of variation in plumage details. The white outer tail feathers flash distinctively in flight and while hopping on the ground. The bill is usually pale pinkish.[12]
Males tend to have darker, more conspicuous markings than females. The dark-eyed junco is 13 to 17.5 cm (5.1 to 6.9 in) long and has a wingspan of 18 to 25 cm (7.1 to 9.8 in).[12][13] Body mass can vary from 18 to 30 g (0.63 to 1.06 oz).[12] Among standard measurements, the wing chord is 6.6 to 9.3 cm (2.6 to 3.7 in), the tail is 6.1 to 7.3 cm (2.4 to 2.9 in), the bill is 0.9 to 1.3 cm (0.35 to 0.51 in) and the tarsus is 1.9 to 2.3 cm (0.75 to 0.91 in).[14] Juveniles often have pale streaks on their underparts and may even be mistaken for vesper sparrows (Pooecetes gramineus) until they acquire adult plumage at 2 to 3 months, but dark-eyed junco fledglings' heads are generally quite uniform in color already, and initially their bills still have conspicuous yellowish edges to the gape, remains of the fleshy wattles that guide the parents when they feed the nestlings.
The song is a trill similar to the chipping sparrow's (Spizella passerina), except that the red-backed dark-eyed junco's (see above) song is more complex, similar to that of the yellow-eyed junco (Junco phaeonotus). The call also resembles that of the black-throated blue warbler (Setophaga caerulescens) which is a member of the New World warbler family.[15] Calls include tick sounds and very high-pitched tinkling chips.[10] It is known among bird song practitioners as an excellent bird to study for learning "bird language."
A sample of the song can be heard at the USGS website[16] (MP3) or at the Cornell Lab of Ornithology website.[17]
The dark-eyed junco's breeding habitat is coniferous or mixed forest areas throughout North America. In otherwise optimal conditions it also utilizes other habitats, but at the southern margin of its range it can only persist in its favorite habitat.[18] Northern birds migrate further south, arriving in their winter quarters between mid-September and November and leaving to breed from mid-March onwards, with almost all of them gone by the end of April or so.[18][19] Many populations are permanent residents or altitudinal migrants, while in cold years they may choose to stay in their winter range and breed there.[18] For example, in the Sierra Nevada Mountains of eastern California, J. hymealis populations will migrate to winter ranges 5,000–7,000 feet (1,500–2,100 m) lower than their summer range. Seasonally sympatric females show difference in migration and reproductive timing that is dependent on hormone and ovary regulation.[20] The migrant female J. hyemails experience delayed growth in the gonad to allow time for their seasonal migration. They then migrate down to the northeastern United States, where the resident subspecies is the Carolina dark-eyed junco (J. h. carolinensis). Female Carolina dark-eyed juncos have large ovaries and, therefore, do not experience gonadal growth delays because they are residents in the area. In winter, dark-eyed juncos are familiar in and around towns, and in many places are the most common birds at feeders.[12] The slate-colored dark-eyed junco (J. h. hyemalis) is a rare vagrant to Western Europe and may successfully winter in Great Britain, usually in domestic gardens.
These birds forage on the ground. In winter, they often forage in flocks that may contain several different subspecies. They mainly eat seeds, supplemented by the occasional insect. A flock of dark-eyed juncos has been known to be called a blizzard.
Dark-eyed juncos usually nest in a cup-shaped depression on the ground, well hidden by vegetation or other material, although nests are sometimes found in the lower branches of a shrub or tree. The nests have an outer diameter of about 10 cm (3.9 in) and are lined with fine grasses and hair. Normally two clutches of four eggs are laid during the breeding season. The slightly glossy eggs are grayish or pale bluish-white and heavily spotted (sometimes splotched) with various shades of brown, purple or gray. The spotting is concentrated at the large end of the egg. The eggs are incubated by the female for 12 to 13 days. The young leave the nest between 11 and 14 days after hatching.[21]
The dark-eyed junco (Junco hyemalis) is a species of junco, a group of small, grayish New World sparrows. This bird is common across much of temperate North America and in summer ranges far into the Arctic. It is a very variable species, much like the related fox sparrow (Passerella iliaca), and its systematics are still not completely untangled.
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