California Partners in Flight Coniferous Forest Bird Conservation Plan Species Account

SPECIES: Dark-eyed Junco, Junco hyemalias

February 2002

Prepared by: Jim DeStaebler, Point Reyes Bird Observatory, jdestaebler@prbo.org

Section 1: Species account outline.

SUBSPECIES STATUS:

Subspecies thurberi is a widespread breeder and winter resident in California. Resident population J. h. pinosus lives in the central coast of California. Western sub-species of the Dark-eyed Junco (DEJU) wintering in California may include J. h. shufeldti which breeds in central and Canadian Rockies and inter-mountain west; J. h. simillus, which breeds on the North-West coast to British Columbia; and J. h. oreganos, which breeds on the pacific coast north of Puget Sound (Pyle 1997). Smaller numbers of other subspecies also regularly occur.

MANAGEMENT STATUS:

No Special status. Protected under the migratory bird act.

Historical references:

• Grinnell and Miller (1944) report breeding DEJU in all California bioregions except Mojave and Colorado Desert. Their range map shows no breeding DEJU in the Sacramento or San Jaquin Valleys or adjacent foothills, in the Great Basin East of Mount Lassen, and most of Southern California south of Monterey county with the exception of isolated mountain ranges and the Sierra Nevada.
• Breeding thurberi were reported in the entirety of Del Norte, Trinity, Humboldt, Mendocino, Sierra, Nevada, Placer, El Dorado, Amador, Calaveras, Alpine, Tuolumne, Mariposa, counties. Breeding thurberi were reported form parts of Siskiyou, Modoc, Lassen, Shasta, Tehama, Butte, Glenn, Yuba, Yolo, Sonoma, Napa, Marin, Tulare, Inyo and Fresno counties.
• Pinosus subspecies was reported as breeding in the entirety of San Francisco and San Mateo counties, parts of Contra Costa, Alameda, Santa Clara, Santa Cruz, Monterey, San Benito, and San Luis Obispo counties. Intergrades with J. h. thurberi in Marin and San Luis Obispo Counties.
• Small population of J. h. caniceps breed in San Bernadino County on Clark Mountain and in Inyo County on Grapevine Mountain near the Nevada border. Formerly a sub-species of the Grey-Headed Junco, it will not be considered in this account.

Current breeding distribution:

Expert opinion:

• McCaskie et al (1979) report DEJU as a common breeder in coniferous Costal and Mountain habitats for Northern California.
• Garrett and Dunn (1980) report DEJU breeding in coniferous and mixed oak-conifer forests in mountain habitats of Southern California. Their range map shows persistence of the isolated inland mountain top populations documented by Grinell and Miller. However, Garrett and Dunn show breeding populations, subspecies unknown, along the coastal plain in San Luis Obispo, Santa Barbara and Ventura counties, where it breeds in mature oak woodlands and eucalyptus groves.
• Survey of breeding avifauna of San Benito Mountain in San Benito County confirms the persistence of breeding pinosus DEJU, and suggests no change from Grinell and Miller (Johnson et al 1985).

Point count: Data not compiled.

Mist netting:

• MAPS data from Sierra Nevada confirms breeding status and suggests the Sierra population is important for species health in California (Siegel and DeSante 1999). Other data not compiled.

Nest searching:

• PRBO data confirms breeding status in the San Bernadino Mts. (PRBO unpbl. data). Other data not compiled.

Spot mapping: Data not compiled

Area search: Data not compiled

Breeding Bird Atlas: With the exception of the Marin County Breeding Bird Atlas, these were not consulted.

BBS Routes: Individual routes were not examined for persistence of breeding populations or range expansions.

ECOLOGY:

Average territory size: 2-3ac per pair in New York (Phelps 1968). See Breeding Density.

Time of occurrence and seasonal movements.

• J. h. pinosus is sedentary, J. h. thurberi is both sedentary and an altitudinal-latitudinal migrant (Grinell and Miller 1944).
• Fall movements recorded from September to December, spring movement from March to May (Phelps 1968).
• Timing of movement of wintering DEJU from outside California not known.
• In the spring, captive males were found to display migratory activity 14 days earlier than females. Conversely, in the fall females displayed zugunruhe 12 days earlier than males, and on average lasted 21 days longer than males (Holberton 1993).
• In Southern California, wintering DEJU arrive late September and leave late April/early May (Garrett and Dunn 1980).
• In Bloomington ID, DEJU defined as on winter home range after December 5 (Nolan and Ketterson 1990).

Arrival date on breeding grounds: In Sierra Nevada, breeding season from early May to mid August (USDA 1980)

Departure date from breeding grounds:

• Spring migration period: Spring migration dates for the west as follows: March and April for California, March 10 to April 5 for Butte Montana, April 13 to May 1 for Prescott Washington, April for Churchill County, Nevada, April 1 for Colorado, April 10 for British Columbia (Bent 1968). Late April, early May (McCaskie et al, 1979).
• Initiation of breeding: May in California, April 22 in Portland Oregon, May 9 for Puget Sound, May 8 for Coeur d’Alene, Idaho. Late dates for nests with eggs are June 8 for Oregon, August 3 for Washington, June 27 for Idaho (Bent 1968).
• Fall migration period: For all migratory sub-species, movement may be regulated by the extent of cold or snow at higher latitudes and elevations and the availability of food.

Extent of wintering in CA:

• Sub-species wintering in California include J. h. shufeldti, J. h. simillus, J. h. oreganus, as well as the two breeding sub-species (Pyle, 1996).
• DEJU winter throughout California, overlapping with breeding range as weather allows. Also winter in Great Basin and interior woodlands and Central Valley, where breeding does not occur.
• In Southern California, winters throughout the coastal lowlands
• More data needed for accurate winter distribution.

Migration stop-over needs/characteristics: no data available

Stop-over period:

• DEJU have considerable post-fledging movement followed by migration to wintering grounds.
• As a short distance and altitudinal migrant, this may involve long direct flights or slow movement in flocks as dictated by weather and food, depending on distance to wintering grounds.
• Location of wintering grounds by sub-species is not known.

Habitat use:

• Suitable fall habitat types encompassed all of 13 Sierran habitat types described in USDA 1980.
• Winter and fall habitat use is characterized by large seed crops, which can sustain flocks of up to hundreds of birds, such as grasses berries and conifers such as Redwood or Douglas-fir, and also Blue Gum.Suitable habitats include edges of chaparral, fence rows bordering farms and ranch lands, juniper and pinon woodlands, sagebrush, city cemeteries, brush tangles, riparian plant growth along streams, suburban yards, orchards, and country roads with weed or brush covered right of way (Bent 1968).
• The presence of edge habitat and the absence of snow are emphasized.

Routes: Low to high elevation movement suggests watercourses and mountain passes may be the typical routes taken (Bent, 1968)

Nest type: Open cup woven with grasses and rootlets, usually on ground, often protected by some large object such as a branch, log or rock (Bent 1968).

Foraging strategy:

• Generalist, mostly seeds and insects on ground.
• Note was made that only Douglas fir seed on the surface of the forest floor were taken, not those inch below the surface, showing that scratching is not a large part of the DEJU foraging strategy (Bent 1968).
• Some other behaviors are noted, including picking fruits, berries or seeds from plants, and hawking insects.

Displays: Breeding courtship displays and flock dynamics both involve flashing the white outer rectrices of the Junco’s tail. In flocks, this may signal age or sex dominance.

Social Organization:

• In fall and winter form flocks, sometimes >100.
• Sex and age segregated wintering grounds are well documented in DEJU (Bent 1968).
• The DEJU is a differential migrant. This is expressed as shorter over wintering period and shorter migration distance for males. Three factors are responsible for this differential migration: body size, social dominance and arrival time. Male’s average larger body size and are shown in lab tests to survive low temperatures better than smaller or female birds. As larger birds, males may be more dominant in a mixed group. If food becomes limited at a site males may out compete females for resources, but separate differential migration eliminates this competition. If males are a shorter distance from the breeding grounds, they are able to return sooner in order to compete for breeding territories.

Typical breeding densities:

• A study of burned coniferous forest plots near Truckee, CA estimated from 18.2 to 9.1 pair/100ha. In burned plots and 17.7 to 13.9 pairs/100ha. in unburned forest over a 25 year period (Raphael 1987).
• An earlier paper from the same study sites at 10 years after the fire estimated 18.4 pairs/100ac on the burned plot and 17.6 pairs/100ac on the unburned plot (Bock 1970).
• In another study with data from Humboldt and Trinity counties, logged plots aged 3-7yr had densities of 42 to 54 pairs/100ac and old growth forest plots had 17 to 19 pairs/100ac (Hagar 1960).
• Bent quoted in USDA 1980 as estimating 2-3 ac/pair in New York.

Mating system:

• Semi-colonial, territorial pairs.
• Pair bonds form in winter flocks or on migration (Bent 1968).
• Adult males have greater site fidelity than females or first year males, both to wintering grounds and breeding territory.
• Delayed breeding (where are immature birds?): Typical passerine, breeds first spring.
• Post fledging biology of offspring (where do they go and when?): As with other passerines breeding in the Sierra Nevada, movement up slope by both adults and juveniles to alpine meadows for post-breeding insect bonanza and pre-basic molt is documented (PRBO data).
• There is a possibility that hatch year males have a more extensive pre-basic molt than females, and divert energy into more extensive molts rather than fat stores and earlier migration (Chandler and Mulvihill 1990).

Clutch size: Three to four eggs in a clutch (Bent 1968). Incubating sex: Female

Incubation period: Nestling period:

Development at hatching: altrical

Number of broods: Two broods not remarkable, though Bent doubted a claim of three of four broods being common.

Who tends the young: Male and female tend young.

Diet: Young are fed insects and vegetable matter.

Major food items:

• Extensive stomach content analysis from NW California shows seasonal and annual variation composed of insects, berries, and grass, weed and Douglas-fir seeds, with insects more numerous in the spring, seed crops in the fall and winter. Reported to be as numerous in freshly logged areas as in old growth and more numerous in regenerating cuts (Hagar1960).
• Arthropods, various seed, some fruit, (USDA 1980).
• Sources allude to the attraction of DEJU to human activities and apparent compatibility with habitat alterations, i.e. foraging in campgrounds and other suburban habitats such as bird feeders.

Wintering ground needs and distribution:

• Widespread throughout California in winter. See Sub-species for wintering sub-species in California.
• Food more than temperature limit wintering flocks (Swanson 1992).
• Dependent on seed crops from annual herbs and grasses, small-seeded conifers, ornamentals and berries.
• More abundant on 3-7yr old woody regenerating plots in winter months than old growth or herbaceous plots (Hagar, 1960).
• Reported winter territory size of 26ac for males and 13 for females (USDA 1980).
• Sex and age segregated flocks are well documented.
• In study in Bloomington ID, wintering birds were segregated north to south: hatch year males, adult males, adult females, and hatch year females (Nolan and Ketterson 1990).
• Suitable fall habitat types encompassed all of 13 Sierran habitat types listed in USDA 1980.
• Suitable habitats include edges of chaparral, fence rows bordering farms and ranch lands, juniper and pinion woodlands, sagebrush, city cemeteries, brush tangles, riparian plant growth along streams, suburban yards, orchards, and country roads with weed or brush covered right of way (Bent 1968).
• The presence of edge habitat and the absence of snow are emphasized.

BREEDING HABITAT AND NEST SITE CHARACTERISTICS:

Overview of breeding habitat:

• Coniferous or mixed conifer/oak woodland with less than complete canopy closure.
• Accounts emphasize the presence of some green herbaceous layer and an edge or transitional quality of the nest locations.
• Associated with the presence of water. "I have never found nesting pairs at any great distance from water" (Bent 1968).
• Study in Colorado Rockies lists the DEJU as abundant in all coniferous forest types (Heil et al).
• Common breeder in almost all forest habitats in Sierra Nevada except pure oak stands, preferring moist openings and edge or meadow habitat with herbaceous undergrowth (Siegel and DeSante 1999, Bent 19xx).
• In Southern California, interior-breeding habitat is mountain coniferous forest, and on the coast mature oak woodland and eucalyptus groves immediately adjacent to the coast (Garrett and Dunn).
• Sources allude to the attraction of DEJU to human activities, i.e. (campgrounds or suburban feeders) and apparent compatibility with habitat alterations i.e. nesting in mailboxes, road cuts, discarded containers and abandoned structures (Bent 1968).

Nest Site.

• Nests on the ground surrounded or near green herbaceous growth, in cup shaped depression in duff, moss or dead grass, woven with grass, pine needles, rootlets and hairs incorporated into the nest, often covered with a log or other protective object. There are occasional reports of nests set in rock faces such as road cuts or elevated off the ground in some way (Bent 1968)

Substrate (species): Data from nest vegetation sampling not compiled

Height of nest: On the ground

Height of plant: Data from nest vegetation sampling not compiled

Nest concealment: Data from nest vegetation sampling not compiled

Vegetation surrounding the nest

Canopy cover: Data from nest vegetation assessment not compiled

Dominant plant species in canopy: coniferous

Average shrub cover:

Dominant shrub species:

Average forb cover:

Dominant forb species:

Ground cover:

Slope:

Aspect:

Tree DBH:

Snags:

Distance to water: near water

Landscape factors

Elevation: Found breeding and wintering at various elevations. Breeding habitat is more related to coniferous woodland and nest substrate than elevation.

Fragmentation: Attracted to edge habitat, clearings and early seral stages. Large-scale removal of forest habitat or land conversion may be harmful (Siegel and DeSante 1999).

Patch size: No data available see territory size.

Disturbance (natural or managed): (e.g. floods, fires, logging)

• Study of burned versus unburned forest plots near Truckee CA found higher densities of breeding Juncos immediately after fire. As shrub and sapling cover came to dominate the burned plot over 25 years, breeding pair density declined from 0.44 pair per hectare to 0.22 pair per hectare, while the control plot fluctuated from 0.44 to 0.34 (Raphael, 1987).
• A study from Humboldt and Trinity Counties suggests the herbaceous and woody regenerating stages after logging are beneficial to Juncos. Higher densities of breeding pairs were found in logged plots than old growth (Hagar, 1960).
• A study from the Colorado Rockies found Juncos to be more abundant in all stages of regenerating clear-cut and commercially thinned forest than in uncut old-growth forest (S.J. Heil et al,).

SPECIAL FACTORS:

Brood parasitisim: Frequency of cowbird parasitism not known.

Dietary: presumed to not limit species health, see foraging above.

Sensitivity to human-induced disturbance: No data available. Use of weedy second growth and suburban habitats for over-wintering may lead to high over-winter mortality from anthropogenic causes. Possible degredation of breeding habitat by grazing and logging.

Pesticide use: No data available.

Predators: As a ground-nesting species, increased predation from mammalian meso-predators could threaten productivity. Attraction to low elevation early succesional habitat for winter could lead to mortality from various suburban sources, i.e. house cats, cars, pollution, children.

Exotic species invasion/encroachment: No data available. As a ground nester dependent on herbaceous vegetation for nest substrate in the breeding season, widespread introduction of exotic annuals could lower productivity.

Other: DeSante reports the apparent drying of the Sierran climate could effect breeding habitat.

POPULATION TREND: http://www.mbr.nbs.gov/bbs/bbs.html

• Negative trends both in California and nation wide for Christmas Bird Count and Breeding Bird Survey.
• In the BBS 1966-1996, nation wide and in California, there was a significant decline in numbers. There were non-significant negative trends in the Sierra Nevada, California foothills and Los Angeles mountain ranges, and Southern California grassland has a non-significant positive trend.
• DEJU are the third most abundant species in BBS after American Robin and Mountain Chickadee (DeSante and George).

DEMOGRAPHICS:

Age and sex ratios: No information available.

Productivity measure(s): Mist-netting indicates high productivity (Siegel and DeSante 1999) though more information is needed.

Survivorship: Mist-netting in the Sierras reports low survivorship (Siegel and DeSante 1999) though more information is needed.

Dispersal: No information on recruitment is available. See migration.

MANAGEMENT ISSUES:

ASSOCIATED SPECIES:

MONITORING METHODS AND RESEARCH NEEDS: Recommend methods that will address immediate needs as well as those most appropriate to monitor how effective the proposed management recommendations will be.

Non-manipulative over-winter survival and flock movement study. Productivity data from nest-searching in a variety of habitats.

Section 2: Action plan summary. Summarize the above information into concise statements under each section.

STATUS (from subspecies, trend, local extirpations, state and federal lists, etc.)

No special status. Protected under migratory songbird act. Significant national and California decline shown in BBS data (1966-1996).

HABITAT NEEDS (e.g., elevation, patch size, breeding habitat characteristics, disturbance):

Breeds at a wide range of elevations in California, from sea level to near tree line. Preferred breeding habitat is moist coniferous forest edge with an herbaceous understory. Responds favorably to early years of forest regeneration. In winter, uses open areas with large seed crops, including fir, redwood, ornamentals, annual forbs and grasses.

CONCERNS (e.g., productivity, brood parasitism, habitat loss, lack of information, wintering distribution, pesticide use)

Common and widespread species with population decline of unknown cause.

OBJECTIVES (e.g., increase distribution, identify healthy breeding populations, increase available habitat, guide restoration efforts to benefit species)

Identify causes of decline.

ACTION (e.g., acquire and restore habitat, specific management and restoration recommendations, specific research and monitoring needs, specific land protection recommendations):

Further data collection or retrieval of data and analysis. Areas of focus should include possible causes of declines, productivity (parasitism and predation, habitat use and assessment, effect of invasive plants) and over-winter survival (flock size and requirements, predation)

SCIENTIFIC REFERENCES:

Bock, C. E. and J. F. Lynch. 1970. Breeding Bird Populations of Burned and Unburned Conifer Forest in the Sierra Nevada. The Condor, 72:182-189

Chandler, C. R. and R. S. Mulvihill. 1990. Wing-shape variation and differential timing of migration in Dark-eyed Juncos. Condor 92:54-61.

DeSante, D. F. and L. T. George. 1994. Population Trends In The Landbirds of Western North America. Studies in Avian Biology No 15:173-190.

Garrett, K. and J. Dunn. 1981. Birds of Southern California: Status and Distribution. Los Angeles Audubon Society.

Hagar, D. C. 1960. Interrelationships of Logging, Birds, Timber Regeneration in the Douglas Fir Region of Northwestern California, Ecology 41( 1): 116-125.

Hejl, S. J. and R. L. Huto, C. R. Preston, and D. M. Finch. The Effects of Silvicultural Treatments in the Rocky Mountains in Ecology and Management of Neotropical Migratory Birds: A Syntheses and Review of Critical Issues. Ed T. E. Martin and D. M. Finch.

Holbertson, R. L. 1993. An Endogenous Basis for Differential Migration In the Dark-Eyed Junco. The Condor 95:580-587

Johnson, N. K. and C. Cicero. 1985. The Breeding Avifauna of San Benito Mountian, California: Evidence for Change over One-Half Century. Western Birds 16(1):1-23.

McCaskie, G, P. De Benedictis, R. Erickson and J. Morlan. 1979. Birds of Northern California: An Annotated Field List. Golden Gate Audubon Society, Berkley CA.

Nolan, V. Jr. and E. D. Ketterson. 1990. Timing of Autumn Migration And Its Relation to Winter Distribution In Dark-eyed Juncos. Ecology 71(4): 1267-1278.

Phelps, J. H., Jr. 1968. Oregon Junco. In A. C. Bent, Life Histories of North American Cardinals, Grosbeaks, Buntings, Towhees, Finches, Sparrows and Allies. O. L. Austin, Editor. Dover Publications, Inc., NY, NY.

Raphael, M. G. and M. L. Morrison, M. P. Yoder-Williams. 1987. Breeding Bird Populations During Twenty-Five Years of Postfire Succession in The Sierra Nevada. The Condor, 89: 614-626.

Sauer, J. R., J. E. Hines, and J. Fallon. 2001. The North American Breeding Bird Survey, Results and Analysis 1966 - 2000. Version 2001.2

Sauer, J. R., S. Schwartz, and B. Hoover. 1996. The Christmas Bird Count Home Page. Version 95.1. Patuxent Wildlife Research Center, Laurel, MD

Siegel, R. B. and D. DeSante. 1999. Version 1.0. The draft avian conservation plan for the Sierra Nevada Bioregion: conservation priorities and strategies for safeguarding Sierra bird populations. Institute for Bird Populations report to California Partners in Flight.

Swanson, D. Seasonal Population Dynamics of Dark-eyed Juncos from Western Oregon. Journal of Field Ornithology, 63(3): 268-275.

California Wildlife and Their Habitats: Western Sierra Nevada. USDA Forest Service Pacific Southwest Forest and Range Experimental Station. General Techincal Report PSW-37. 1980.