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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 (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
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
There are no known adverse affects of dark-eyed juncos on humans.
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
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
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 (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 )
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
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.
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.
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:
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)
