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dark-eyed junco

Junco hyemalis

What do they look like?

Dark-eyed juncos are small birds that are 12.5 to 16.5 cm long. They weigh about 19 g and have a wingspan of about 23.5 cm. They have a dark gray head, back and breast and a very white belly. Their tails are dark gray on the middle feathers and white on the outside feathers. Dark-eyed juncos have a pink bill and dark eyes.

Female dark-eyed juncos are a little bit smaller and browner than males. Young juncos are also browner than males, and they have streaks on their breast. (Barrowclough, 1983; Reader's Digest Association, 1991; Sibley, 2000; Sullivan, 1999)

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • Average mass
    19 g
    0.67 oz
  • Average mass
    18 g
    0.63 oz
    AnAge
  • Range length
    12.5 to 16.5 cm
    4.92 to 6.50 in
  • Average wingspan
    23.5 cm
    9.25 in
  • Average basal metabolic rate
    46 cm3.O2/g/hr
  • Average basal metabolic rate
    0.2959 W
    AnAge

Where do they live?

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. (United States Department of Agriculture, 1991)

What kind of habitat do they need?

Dark-eyed juncos are found in woodlands that have openings with a dense layer of plants near the ground. They avoid going deep into forests. Instead, they prefer openings and the edges of forests and woodlands. In winter, they can be found in weedy fields, open woodlands, hedgerows, suburbs, and farmyards. They live between sea level and 3500 meters elevation. (Nolan, et al., 2002; United States Department of Agriculture, 1991)

  • Range elevation
    0 to 3500 m
    0.00 to 11482.94 ft

How do they reproduce?

Dark-eyed juncos are monogamous. Males arrive at the breeding grounds very early in the spring. They claim a territory by singing from the top of the tallest trees in a 2 to 3 acre area. When a female enters a territory, the male follows her around. He spreads his tail and wings and struts around the female, making "chip" sounds and singing. He may move his tail up and down to show off his white feathers to the female. Males and females form pairs by mid-April. The males follow their mates around and usually stay within 50 feet of the female. (Bent and et al, 1968; Kennedy, 2002; Nolan, et al., 2002; Sullivan, 1999)

Dark-eyed juncos begin breeding in April. The female builds the nest and the male helps by bringing nest material. Nests are usually built on the ground near the edge of a forest opening. They are usually hidden under plants, logs, tree roots, or other shelters. Nests are sometimes built in a tree or shrub up to 8 feet above the ground. They are built of sticks, leaves and moss, and are lined with soft materials, like grasses, mosses or mammal hair. Each nest can be used to raise two or three broods in one season.

The female lays 3 to 6 white or greenish eggs with brown spots. The eggs are usually slightly glossy and about 19 mm long. The female incubates the eggs for 12 to 13 days. The chicks are helpless when they hatch, but they are able to leave the nest after 9 to 13 days. The parents feed the chicks while they are in the nest and for about 3 weeks after they have left the nest. Most dark-eyed juncos begin breeding when they are 1 year old. (Bent and et al, 1968; Brewer, et al., 1991; Nolan, et al., 2002; Reader's Digest Association, 1991; Sullivan, 1999; United States Department of Agriculture, 1991)

  • How often does reproduction occur?
    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 eggs per season
    4
    AnAge
  • Average time to hatching
    12 to 13 days
  • Average time to hatching
    11 days
    AnAge
  • 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

The female parent incubates the eggs and broods the chicks after they hatch. Both parents defend the nest from predators and clean the nest by removing fecal sacs. They also feed the chicks regurgitated food and soft insects, such as caterpillars.

Chicks are helpless (altricial) when they hatch. Their eyes begin to open after 2 days and they begin to grow feathers after 7 days. They develop strong leg muscles before they can fly so that they can run away from predators. They leave the nest after 9 to 13 days. The parents still feed the chicks for about 3 weeks after they leave the nest. If chicks beg from their parents after 3 weeks, the parents will chase them away. (Bent and et al, 1968; Kennedy, 2002; Reader's Digest Association, 1991)

  • 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

How long do they live?

Dark-eyed juncos usually live between 3 and 11 years. The oldest known wild dark-eyed junco lived at least 11 years and 1 month. Most juncos probably die due to predation by other species (hawks, squirrels, weasels, etc.). (Nolan, et al., 2002; The Norman Bird Sanctuary, 2000)

  • Range lifespan
    Status: wild
    11.1 (high) years
  • Typical lifespan
    Status: wild
    3 to 11 years

How do they behave?

Dark-eyed juncos usually hop or walk to move along the ground. They are social during autumn and winter. During these months, juncos spend the days in flocks of 15 to 25 birds. These flocks are often found with flocks of American tree sparrows (Spizella arborea).

Dark-eyed juncos usually migrate to the same area every winter. Each flock stays in an area about 10 to 12 acres in size. There is a social hierarchy within the winter flocks. Males are dominant over females and adults are dominant over the younger birds. Dominant birds rush at or peck at other birds to chase them away.

Juncos spend most of their time either perching or looking for food. During the summer, they spend about 4.5 hours each day looking for food. In the winter, they need more energy to keep warm, so they spend about 6 hours each day looking for food.

Most dark-eyed junco populations are migratory. However, some populations are sedentary or partially migratory. (Bent and et al, 1968; McPeek, 1994; Sibley, 2000; Stokes Nature Company, 2002; Sullivan, 1999)

  • Range territory size
    10,000 to 20,000 m^2

Home Range

Winter flocks have a home range of 10 to 12 acres. (Sullivan, 1999; United States Department of Agriculture, 2002)

How do they communicate with each other?

Dark-eyed juncos have many different songs. Their most common song is a simple, musical trill. Only male dark-eyed juncos sing. To show that they own a territory, males use a warbling song. They use different calls when they are alarmed or when fighting or scolding another.

Dark-eyed juncos also use physical displays to show ownership of a territory and to attract a mate. (Bent and et al, 1968; Sullivan, 1999)

What do they eat?

Dark-eyed juncos eat insects, non-insect arthropods, and seeds during the fall and winter. They are often seen at bird feeders during migration and in the winter months, but they prefer to search for food on the ground. When there is snow on the ground, dark-eyed juncos scratch away a small circle of snow to look for grain. To eat grass seed, dark-eyed juncos "ride" a grass stem. They fly to a tall grass stem and hold on as the stem bends down to the ground. The junco can stand on the grass stem on the ground and eat the seeds. During the breeding season, dark-eyed juncos eat mostly insects, including caterpillars, beetles, and ants. They also eat the seeds of many weed species.

Dark-eyed juncos drink water from streams or pools or from raindrops or dew on plant leaves. During the winter, they eat snow in order to get water. (Bent and et al, 1968; Dunning, 2001; McPeek, 1994; Sullivan, 1999; United States Department of Agriculture, 1991)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • seeds, grains, and nuts

What eats them and how do they avoid being eaten?

Dark-eyed juncos are killed by many different birds, including sharp-shinned hawks, shrikes and owls. They are also often 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.

When a predator approaches, dark-eyed juncos hide under whatever is nearby. If a predator comes near a nest, parents make "chip" sounds and fly around the nest area. They sometimes even dive at predators. (Bent and et al, 1968; Sullivan, 1999; United States Department of Agriculture, 2002)

What roles do they have in the ecosystem?

Dark-eyed juncos play an important role in their ecosystems. They disperse seeds and help to control insect populations. Brown-headed cowbirds (Molothrus ater) sometimes lay their eggs in the nests of dark-eyed juncos. When this happens, the dark-eyed junco parents feed and protect the brown-headed cowbird chicks. Dark-eyed juncos also host many different parasites. (Bent and et al, 1968; Nolan, et al., 2002)

  • Ecosystem Impact
  • disperses seeds

Do they cause problems?

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

How do they interact with us?

Dark-eyed juncos do not really affect humans, though many people enjoy photographing them or watching them at bird feeders. They also eat some insects that are pests. (Bent and et al, 1968)

  • Ways that people benefit from these animals:
  • controls pest population

Are they endangered?

Dark-eyed juncos are protected under the US Migratory Bird Treaty Act. They are very common birds.

Some more information...

There are a few subspecies of dark-eyed juncos. These subspecies look a little bit different from each other, but they often breed together. Some of the subspecies of dark-eyed juncos are the "Slate-colored" Junco, the "White-winged" Junco, Oregon Junco, and the "Gray-headed" Junco. (Barrowclough, 1983; Sibley, 2000)

Contributors

Alaine Camfield (editor), Animal Diversity Web.

Kari Kirschbaum (editor), Animal Diversity Web.

Aynsley Carroll (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

References

Barrowclough, F. 1983. The Audubon Society Master Guide to Birding: Vol. 3. New York: Knopf.

Bent, A., et al. 1968. Life Histories of North American Cardinals, Grosbeaks, Buntings, Towhees, Finches, Sparrows, and Allies: Part II. New York: Dover Publications.

Brewer, R., G. McPeek, R. Adams. 1991. The Atlas of Breeding Birds in Michigan. Lansing: Michigan State University Press.

Dunning, J. 2001. New World Sparrows. Pp. 516-535 in C Elphick, J Dunning, D Sibley, eds. The Sibley Guide to Bird Life and Behavior. New York: Alfred A. Knopf.

Kennedy, D. 2002. "Birds of Stanford" (On-line). Stanford Alumni Association. Accessed March 23, 2004 at http://www.stanfordalumni.org/birdsite/.

McPeek, G. 1994. The Birds of Michigan. Indiana: University Press.

National Audubon Society, 1994. National Audubon Society Field Guide to North American Birds - Eastern Region. New York: Knopf.

Nolan, V., E. Keterson, D. Cristol, C. Rogers, E. Clotfelter, R. Titus, S. Schoech, E. Snajdr. 2002. Dark-eyed junco (Junco hyemalis). Pp. 1-44 in A Poole, F Gill, eds. The Birds of North America, Vol. 716. Philadelphia, PA: The Birds of North America, Inc.

Reader's Digest Association, 1991. Book of North American Birds. New York: Reader's Digest Association, Inc.

Sibley, D. 2000. The Sibley Guide to Birds. New York: Knopf.

Stokes Nature Company, 2002. "Bird Behavior" (On-line). Stokes Birds. Accessed March 23, 2004 at http://www.stokesbirdsathome.com/birding/behav/behavpages/behav110.html.

Sullivan, K. 1999. Yellow-eyed Junco. The Birds of North America, No. 464, 1999, No. 464: 1-23.

The Norman Bird Sanctuary, 2000. "The Norman Bird Sanctuary" (On-line). Accessed March 23, 2004 at http://www.normanbirdsanctuary.org/articles/darkeyedjunco01.shtml.

United States Department of Agriculture, 1991. Forest and Rangeland Birds of the United States - Natural History and Habitat Use. United States Department of Agriculture Forest Service Agriculture Handbook 688.

United States Department of Agriculture, 2002. "Integrated Taxonomic Information Center" (On-line). Accessed March 23, 2004 at http://www.itis.usda.gov/.

 
University of Michigan Museum of ZoologyNational Science Foundation

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Carroll, A. 2004. "Junco hyemalis" (On-line), Animal Diversity Web. Accessed September 19, 2014 at http://www.biokids.umich.edu/accounts/Junco_hyemalis/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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