Fox Sparrow (Passerella iliaca)

Prepared by: Anne King

Maps

References
Action Plan Summary

SUBSPECIES STATUS

The eighteen subspecies of Fox Sparrows are divided into four main groups: Red Fox Sparrow (iliaca) group, Sooty Fox Sparrow (unalaschensis) group, Slate-colored Fox Sparrow (schistacea) group, and Thick-billed Fox Sparrow (megarhyncha) group (Zink and Kessen 1999).

All five subspecies of the Thick-billed group (P. i. fulva, P. i. brevicauda, P. i. megarhyncha, P. i. stephensi, and P. i. monoensis) and one subspecies of the Slate-colored group (P. i. canscens) breed in California (Zink and Kessen 1999).

All of the Thick-billed subspecies also appear to winter in California, though most individuals of P. i. stephensi winter out of state (Grinnell and Miller 1944, Small 1994, Pyle 1997).In addition, all six of the Sooty subspecies (P. i. annectens, P. i. fulginosa, P. i. insularis, P. i. sinuosa, P. i. townsendi, and P. i. unalaschensis), four of the five Slate-colored subspecies (P. i. altivagans, P. i. canescens, P. i. olivacea, and P. i. schistacea), and one of the Red subspecies (P. i. zaboria) winter in California (Pyle 1997).

MANAGEMENT STATUS

Fox Sparrow is not afforded any official status by the US Fish and Wildlife Service or the California Department of Fish and Game.

RANGE MAPS (California):Information on historical distribution and abundance.Information on current distribution (especially breeding).

I. Historical references

Historically, six subspecies of Fox Sparrow nested throughout California.Breeding populations primarily occurred along the southern Cascade, Sierra Nevada, Siskiyou, Klamath, Salmon, Trinity, Inyo, and White mountains, the northern Coast Ranges, and several isolated mountains in southern California (see Grinnell and Miller 1944 for map of historic breding distribution).Except for P. i. canescens which occurred in small numbers, all were common to abundant within their given range.

Historical breeding records document nesting populations in the Lassen Peak region (Grinnell et al. 1928), in the eastern Sierra Nevada of Nevada County (Bock and Lynch 1970), at Lake Tahoe (Mailliard 1921), at the headwaters of the American River in Placer County (Beedy 1981), and at Big Bear Lake in San Bernardino County (Pierce 1921).

II. Current breeding distribution

All six historically breeding subspecies currently nest in montane areas of the state, occupying a breeding range very similar to that of the historical range (see Zink and Kessen 1999 for map of current breeding distribution).P. i. brevicauda breeds in the inner Coast Range from Trinity and east-central Humboldt counties south to Colusa County; P. i. megarhyncha breeds from the Siskiyou Mountains south through the Cascades-Sierra axis to Fresno and Inyo counties; P. i. fulva breeds in the Warner Mountians, Modoc Plateau, and the Cascades of western Lassen County; P. i. monoensis breeds on the eastern slopes of the Sierra Nevada from Alpine County south to the southern rim of the Mono Basin; P. i. canescens breeds in the White and Inyo mountains; and P. i. stephensi breeds on the western slopes of the southern Sierra Nevada from southern Fresno County south to the Greenhorn Mountains of Kern and Tulare counties, the Mount Pinos area of Kern and Ventura counties, the Transverse Ranges and the San Jacinto Mountain area, Big Pine Mountain in San Bernardino County, and Palomar Mountain and Cuyamaca Peak in San Diego County (Small 1994).

A. Sites known to contain breeding populations: including type of data and year(s) collected

Lassen National Forest (Mill Creek, Gurnsey Creek, and Upper Butt Creek drainages): point counting, spot mapping, and mist netting in 1997-1999 (King et al. 2000).

Yosemite National Park, Sierra National Forest, Kings Canyon National Park, and Sequoia National Park: point counting in 1983-1985 (Hejl et al. 1988).

Numerous locations in the Yosemite area and adjacent east slope of the Sierra Nevada: expert opinion (Gaines 1988).

Eastern Sierra Nevada (13 km north of Truckee): spot mapping in 1981-1985 (Raphael et al. 1987).

Sequoia National Forest (7.5 km northwest of Hume - 36°48´N, 118°59´W): nest monitoring in 1989 (Burns and Hackett 1993).

San Bernardino National Forest: nest monitoring in 1992-1997 (PRBO data).

Breeding Bird Survey data from 1989-1998 shows averages of at least 1.0 individual per route on 29 routes in Del Norte, Lake, Siskiyou, Shasta, Lassen, Butte, Sierra, Placer, El Dorado, Amador, Alpine, Tuolumne, Tulare, Fresno, Kern, Inyo, Ventura, and Los Angeles counties (Sauer et al. 1998).The highest densities (>10 individuals per route) were recorded at Ship Mountain (Del Norte), McCloud (Siskiyou), Mount Shasta (Siskiyou), Hat Creek (Shasta), Downieville (Sierra), Riverton (El Dorado), Pilot Creek (El Dorado), Tahoe National Forest, Westville (Placer), Johnsville (Placer), Dardanelle (Tuolumne), Lakeshore (Fresno), Greenhorn Mountain (Kern), and Angeles National Forest.

ECOLOGY

I.Average territory size:no information.

II.Time of occurrence and seasonal movements

A.Arrival date on breeding grounds

Most populations arrive on breeding grounds in mid-April, though breeding populations in the Coast Range arrive in May (Small 1994).

B.Departure date from breeding grounds: early to mid-September (Small 1994).

C. Spring migration period

Due to the short migration distance, this period is relatively short for subspecies breeding and wintering in California.Generally, they depart the wintering grounds in April and arrive on the breeding grounds in mid-April and May.Subspecies wintering in California but breeding elsewhere depart the wintering grounds in mid-April (Small 1994).

D. Fall migration period

As with spring migration, this period is relatively short, with subspecies resident to California departing the breeding grounds in early to mid-September and arriving on the wintering grounds in mid- to late September.Winter residents arrive from breeding grounds out of state in mid-September (Small 1994).

E. Extent of wintering in CA

Wintering areas for 16 subspecies are located in the foothills and lowlands throughout the state, except for the eastern and southeastern deserts (Small 1994).

III. Migration stop-over needs/characteristics

A. Stop-over period:no information.

B. Habitat use:favor shrubby areas during migration, but are found in wide variety of habitats, including riparian, chaparral, sagebrush scrub, and residential gardens (Gaines 1988).

C. Routes:Subspecies breeding in Alaska and wintering in California may use transoceanic migratory route (Bell 1997).No information on route of short distant migrants breeding and wintering in California.

III. Nest type

Bulky, well constructed deep cup, built by female over 2Ė3 days.Made of grass, moss, lichen, rootlets, shredded bark, wood chips, and leaves; twigs also used if built above ground.Nest is lined with fine grass, hair, rootlets, fur, feathers, and finely shredded bark (Harrison 1979, Ehrlich et al. 1988, Baicich and Harrison 1997). 

IV. Foraging strategy

Feed primarily on the ground, scratching for insects and seeds, particularly in leaf litter (Grinnel and Miller 1944, Rising 1996).

VI. Displays

When available, males sing from tops of small trees, usually young conifers, and other perches projecting above the shrubby areas in which they nest.Otherwise, they sing from perches in the shrubs or on the ground (Grinnell et al. 1930, Grinnell and Miller 1944, Rising 1996).Females will give broken-wing display near a nest (Rising 1996), and adults are know to do the same in defense of young fledgling (Ehrlich et al. 1988).

VII. Social Organization

A. Typical breeding densities

Bock and Lynch (1970) reported densities of 1.2 pairs per 100 acres on a burned study plot and 0.9 pairs per 100 acres on an unburned plot in 1966-1968.

Beedy (1981) recorded densities of 5-16 individuals per 40 hectares, with highest densities in open canopy forest, particularly red fir.

B. Mating system:probably monogamous (Ehrlich et al. 1988).

C. Delayed breeding (where are immature birds?):no information.

D. Post fledging biology of offspring (where do they go and when?):no information.

E. Post breeding social behavior (mixed species flocks, or simply migrate away?):no information.

VI. Clutch size

Usually 3-4, but range is 2-5; averages 4-5 in northern part of range and 2-3 in southern part of range (Ehrlich et al. 1988, Rising 1996, Baicich and Harrison 1997).

VII. Incubating sex:Female (Ehrlich et al. 1988, Rising 1996, Baicich and Harrison 1997).

VIII. Incubation period:12-14 days (Rising 1996, Baicich and Harrison 1997).Mailliard observed females beginning incubation after laying their first egg (Mailliard 1921).

IX. Nestling period:9-11 days (Ehrlich et al. 1988, Baicich and Harrison 1997).

XII. Development at hatching:Nestlings are altricial (Ehrlich et al. 1988); no additional information available.

XIII. Number of broods

Brood once (Harrison 1979), though double brooding in subspecies that nest outside of California is suspected (Linsdale 1920).

XIV. Who tends the young

Both the male and female tend the young (Ehrlich et al. 1988, Rising 1996, Baicich and Harrison 1997).However, Grinnell et al. (1930) reported that at a nest watched for most of one day, the female made trips to the nest with food at intervals of 2-5 minutes, while the male only took food to the nest twice.At another nest, the male was observed carrying food to the female, who then carried it to the nest.

XV. Diet

A. Major food items (by season)

Generally feed on insects, seeds, and berries, with a preference for weed seeds outside of the breeding season (Bent 1968, Ehrlich et al. 1988).Stomach contents of two P . i. megarhyncha individuals collected in April were filled almost entirely with weed seeds (Linsdale 1920).Nestlings are likely fed 100% insects (Ehrlich et al. 1988), though a female was observed feeding nestlings leaves of Minerís lettuce (Grinnell et al. 1930).

B. Drinking:no information.

XVI. Wintering ground needs and distribution

Fox Sparrows winter in chaparral and streamside thickets of foothill and lowland areas throughout California, except for the eastern and southeastern deserts (Small 1994 and Rising 1996).

BREEDING HABITAT AND NEST SITE CHARACTERISTICS

I. Overview of breeding habitat: (e.g. oak woodland vs. oak savannah, age of stand, dominant species, plant species diversity, structural diversity/variability) 

Fox Sparrows are found primarily in low, dense scrub, sometimes interspersed with scattered or open stands of trees, and, less frequently, in riparian thickets (Gaines 1988, Small 1994).Scrub habitat is generally dominated by Ceanothus, manzanita, chinquapin, gooseberry, and cherry, while riparian thickets consist primarily of willow and aspen shrubs (Grinnell and Miller 1944, Gaines 1988, Small 1994).Although plant species associated with Fox Sparrow habitat may vary with elevation and geography, the preferred nesting habitat is consistently dense and brushy (Small 1994).

II. Nest Site

Information on nest sites is based on 1) 26 nests near Big Bear, San Bernardino County (SB) in 1994-1996 (PRBO unpublished data); 2) 8 nests near Big Bear Lake, San Bernardino County in 1919-1920 (Pierce 1921); 3) 25 nests near Hume, Fresno County in 1989 (Burns and Hackett 1993); 3) 14 nests near Lake Tahoe in 1920 (Mailliard 1921); and 5) 5 nests near Mineral, Tehama County in 1925-1929 (Grinnell et al. 1930).

A. Substrate (species)

At SB, all Pierce nests were in or under mountain whitethorn.

At SB, PRBO nests were in or under mountain whitethorn (39%), chinquapin (28%), gooseberry (12%), willow (9%), white fir, manzanita, and grass (4% each).

Near Hume, the majority of nests (59%) were located in or under mountain whitethorn, 18.5% were in or under green-leaf manzanitas, 14.8% were associated with bush chinquapin, 3.7% were under Sierra gooseberry, and 3.7% were in willows.

At Lake Tahoe, ground nests were built under a variety of substrates, including Douglas fir, chinquapin, oak, Ceanothus species, and bark.Remaining nests were built in Ceanothus species, willow, gooseberry, and dead willow and aspen.

All nests near Mineral were in mountain whitethorn.

B. Height of nest

At SB, 38% of Pierceís nests were on the ground, and the remaining 5 were 15 cm to 1 m above ground.

At SB, 46% of PRBO nests were on the ground, and the remaining 14 varied in height from 10 cm to 1 m.

Near Hume, 61% of nests were on the ground, and the mean height of the other nests was 30 cm.

At Lake Tahoe, 43% of nests were on the ground, and the remaining 8 ranged from 25 cm to 1.1 m.

Near Mineral, nests were located 14 Ė 53 cm above the ground.

C. Height of plant

At SB, the majority of PRBO nest plants were 1-2 meters in height, except one of 0.75 m and another of 6 m.

The mean height of nest plants near Hume was 1.41 meters.

D. Nest concealment

At SB, concealment at PRBO nests ranged from 50-100%, with an average concealment of 90%.

Near Hume, 40% of the of the nests were completely concealed, 32% were 75% concealed, 12% were 50% concealed, and 16% were completely visible.

III. Vegetation surrounding the nest (Importance of each category may differ by species)

Information on vegetation surrounding nest sites is based on 1) data collected at 19 nest sites near Big Bear, San Bernardino County (SB) in 1994-1996 (PRBO unpublished data); and 2) data collected at 25 nest sites near Hume, Fresno County in 1989 (Burns and Hackett 1993).

A. Canopy cover:based on averaged densiometer readings

Canopy cover at SB ranged from 3.44% to 81%, with an average of 34%

B. Dominant plant species in canopy:

Dominant canopy species at SB were Jeffery pine and white fir, with at least one of these present within an 11.3 meter radius of 13 of 19 nest sites.

C. Average shrub cover:

Shrub cover within a 5 meter radius of SB nests ranged from 10% to 100% with an average of 86%.

D. Dominant shrub species:

Dominant shrub species within a 5 meter radius of SB nests were mountain whitethorn, manzanita, and gooseberry.Dominant species within a 4 meter radius of nests near Hume were mountain whitethorn, green-leaf manzanita, and bushchinquapin.

E. Average forb cover:no information.

F. Dominant forb species: no information.

G. Ground cover

Ground cover within a 5 meter radius of SB nests consisted primarily of green cover (average of 67%) and litter (average of 23%).Green ground cover was primarily shrub (average of 84%) with some forb and fern cover.

H. Slope

Slope at SB nest sites ranged from 1% to 47%, though most were less than 10%.

I. Aspect

Nests at SB occurred on slopes with a wide range of aspects, though the highest percentage (37%) had a NW orientation.

J. Tree DBH

Trees within an 11.3 meter radius of nests at SB were relatively evenly distributed in 3 DBH ranges of 8-23 cm, 23-38 cm, and greater than 38 cm.

K. Snags

No snags were present within an 11.3 meter radius of nests at SB, though stumps were present within an 11.3 meter radius of 3 out of 19 nest sites.

L. Distance to water:no available information

IV. Landscape factors

A. Elevation

Breeding sites range in altitude from 3,500 feet near Mount Shasta in Siskiyou County to 10,000 feet on San Jacinto Mountain in San Bernardino County.

B. Fragmentation:no information.

C. Patch size:no information.

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

Fox Sparrow and other shrub nesting species increased after a fire in the eastern Sierra Nevada (Raphael et al. 1987), though they were absent in severely burned areas in the Rockies (Hejl 1994).

E. Adjacent land use:no information.

F.Other:no information.

SPECIAL FACTORS:Factors influencing a species occurrence and viability.

I. Brood parasitism

Generally considered uncommon to occasional Brown-headed Cowbird host (Ehrlich et al. 1988, Rising 1996).However, Airola (1986) reported much higher parasitism rates in disturbed areas of the northern Sierra Nevada. Based on observations primarily of family groups with dependent young, parasitism was documented in 7 of 9 records. 

II. Dietary:no information.

III. Sensitivity to human-induced disturbance:no information.

IV. Pesticide use:no information.

V. Predators:Primary nest predator is Stellerís Jay (Bent 1968).

VI. Exotic species invasion/encroachment:no information.

VII. Other:no information.

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

Results from Breeding Bird Survey (BBS) routes throughout California (42 routes) and specifically in the Sierra Nevada region (20 routes) do not indicate any significant trends in Fox Sparrow detections between 1966 and 1998.

However, recent results from historic breeding sites in the Yosemite and Lassen areas indicate that populations in these areas have declined markedly (Beedy 1982, King et al. 2000).

DEMOGRAPHICS

I. Age and sex ratios:no information.

II. Productivity measure(s):

Monitoring of 26 nests near Big Bear, San Bernardino County documented a success rate of 42% (PRBO unpublished data).

III. Survivorship:no information.

IV. Dispersal:no information.

MANAGEMENT ISSUES

The primary management issue for Fox Sparrows is fire suppression.Hehl (1994) stated that the exclusion of fire has been the most significant factor affecting todayís western forests.As a result of fire suppression, the structure of western forests has changed dramatically over the past 50-100 years.Fire suppression and logging appear to have reduced the number of large trees and increased the density of smaller and understory trees, particularly white fir (Agee et al. 1978, Husari 1980, Chang 1996).The primary results have been decreases in structural diversity, species diversity, and shrub cover. This has resulted in very dense homogenous forests with closed canopies and little shrub cover.This has had negative impacts on Fox Sparrows, and other species, require openings in coniferous forest with high shrub cover or relatively open canopy forest with a shrub understory (Beedy 1982, King et al. 2000).

ASSOCIATED SPECIES:A list of other species that would benefit from management of the target species.

Species that would benefit most directly from efforts to increase preferred Fox Sparrow habitat are:

Green-tailed Towhee 

Dusky Flycatcher

Many additional species that are more abundant in open canopy coniferous forest than closed canopy forest (Beedy 1981) are also expected to benefit, including:

Western Wood-pewee

Olive-sided Flycatcher

Hermit Thrush

Ruby-crowned Kinglet

Warbling Vireo

Nashville Warbler

Audubonís Warbler

Hermit Warbler

Wilsonís Warbler

Western Tanager

Evening Grosbeak

Oregon Junco

Chipping Sparrow

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.

The immediate need is to gain a better understanding of current breeding populations and current status of historic breeding populations.This could be accomplished by comprehensive surveys at historical breeding sites and in other suitable habitat.

Monitoring of these populations (nest monitoring, vegetation assessment, GIS mapping, etc.) would add to the small amount of information on productivity, specific habitat requirements and landscape factors.It would also provide evaluation of efforts to restore natural fire cycles. 



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.)

Although BBS data does not indicate a declining trend and Fox Sparrow is not on any state or federal lists, several studies have reported local declines and extirpation (Beedy et al. 1982, King et al. 2000).It is likely that other local declines and/or extirpations have occurred but are not documented.

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

Fox Sparrows occur at high elevations (3,500-10,000 feet) and require forested or open habitat with substantial shrub cover.No information on required patch size or disturbance is available.

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

The primary concerns are habitat loss and lack of information.The management practice of fire suppression has altered forest habitat dramatically, through changes in forest structure and reduction of shrub cover.These changes have been to the detriment of many species, including Fox Sparrow.

Very little work has been done on Fox Sparrows, and information on specific habitat requirements (i.e. patch size), landscape factors, and other requirements is available.In addition, there is limited documentation of current nesting populations and historic breeding populations should be revisted to update their status.Data on productivity and survivorship is almost entirely lacking.

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

The primary objectives should be to increase available habitat, identify and assess health of current breeding populations, and provide information on population and landscape characteristic that are lacking.

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

Many agencies have already established the objective of restoring natural fire cycles and forest structure, though the importance of this goal should be stressed.It will likely be a very long process, but it would benefit Fox Sparrows and many other bird species in the long run.

Identification of current breeding populations could be achieved through comprehensive surveys of historic breeding sites and other areas of suitable habitat.Assessment of historic breeding sites should be conducted to determine if these populations have declined or been extirpated.Once current breeding populations are identified, their health could be evaluated through monitoring and information on specific habitat and landscape characteristics could be gathered. 



SCIENTIFIC REFERENCES:

Agee, J. K., R. H. Wakimoto, and H. H. Biswell.1978. Fire and fuel dynamics of Sierra Nevada conifers.Forest Ecology and Management 1: 255-265.

Airola, D. A. 1986.Brown-headed cowbird parasitism and habitat disturbance in the Sierra Nevada.Journal of Wildlife Management 50(4):571-575.

Baicich, P. J. and C. J. O. Harrison.1997.A guide to the nests, eggs, and nestlings of North American Birds, second edition.Academic Press, San Diego, CA.

Beedy, E. C.1981.Bird communities and forest structure in the Sierra Nevada of California.Condor 83:97-105.

Beedy, E. C.1982.Bird community structure in coniferous forests of Yosemite National Park, California.Ph.D. dissertation, University of California, Davis.

Bell, C. P.1997.Leap-frog migration in the Fox Sparrow: Minimizing the cost of spring migration.Condor 99:470-477.

Bent, A. C.1968.Life histories of North American cardinals, grosbeaks, buntings, towhees, finches, sparrows, and allies, Part 3.Smithsonian Institute Press, Washington, DC.

Bock, C. E. and J. F. Lynch.1970.Breeding bird populations of burned and unburned conifer forest in the Sierra Nevada.Condor 72:182-189.

Burns, K. J. and S. J. Hackett.Nest and nest-site characteristics of a western population of Fox Sparrow (Passerella iliaca).The Southwestern Naturalist 38(3):277-279.

Chang, C.1996. Ecosystem responses to fore and variations in fore regimes.Sierra Nevada Ecosystem Project, Final Report to Congress, V II, Assessments and Scientific Basis for Management Options. University of California, Davis.

Ehrlich, P. R., D. S. Dobkin, and D. Wheye.1988.The Birderís Handbook: A field guide to the natural history of North American birds.Simon and Schuster Inc., New York, New York.

Gaines, D. 1988.Birds of Yosemite and the East Slope.Artemesia Press, Lee Vining, CA.

Grinnell, J., J. Dixon, and J. M. Linsdale.1930.Vertebrate natural history of a section of northern Californi through the Lassen Peak region.University of California Press, Berkeley, CA.

Grinnell, J. and A. H. Miller. 1944.The distribution of the birds of California.Pacific Coast Avifauna Number 7.Cooper Ornithological Club, Berkeley, CA.Reprinted by Artemesia Press, Lee Vining, CA.

Harrison, H. H.Western birdsí nests.1979.Houghton Mifflin Company, New York, NY.

Hejl, S. J., J. Verner, and R. P. Balda.1988.Weather and bird populations in true fir forests of the Sierra Nevada, California.1988.Condor 90:561-574.

Hejl, S. J.1994.Human induced changes in bird populations in coniferous forests in western North America during the past 100 years.Studies in Avian Biology 15:232-246.

Husari, S. J.1980. Fire ecology of the vegetative habitat types in the Lassen Fire Management Planning Area (Caribou Wilderness and Lassen Volcanic National Park).In Fire Management Plan: Lassen management planning area park, Caribou unit.Lassen Volcanic National Park and Lassen National Forest.

King, A. K., J. R. King, and N. Nur.Songbird monitoring in the Almanor Ranger District (Lassen National Forest) and Lassen Volcanic National Park: 1997-1999.Unpublished Point Reyes Bird Observatory report to the US Forest Service and National Park Service.

Linsdale, J. M.1920.Variations in the Fox Sparrow (Passerella iliaca) with reference to natural history and osteology.University of California Publications in Zoology 30:251-392.

Mailliard, J. W.1921.Notes on the nesting of the Yosemite Fox Sparrow, Calliope Hummingbird, and Western Wood-pewee at Lake Tahoe, California.Condor 23(3):73-78.

Pierce, W. M.1921.Nesting of the Stephens Fox Sparrow. Condor 23(3):80-85

Pyle, P. 1997.Identification guide to North American birds, Part 1.Slate Creek Prees, Bolinas, CA.

Raphael, M. G., M. L.Morrison, and M. P. Yoder-Williams.1987.Breeding bird populations during twenty-five years of postfire succession in the Sierra Nevada.Condor 89:614-626.

Rising, J. D. 1996.A guide to the identification and natural history of the sparrows of the United States and Canada.Academic Press, Inc., San Diego, CA.

Sauer, J. R., J. E. Hines, I. Thomas, J. Fallon, and G. Gough. 1999. The North American Breeding Bird Survey, Results and Analysis 1966 - 1998. Version 98.1, USGS Patuxent Wildlife Research Center, Laurel, MD.

Small, A. 1994.California birds: their status and distribution.Ibis Publishing Company, Vista, CA. 

Zink, R. M. and A. E. Kessen.1999.Species limits in the Fox Sparrow.Birding 31(6):508-517.


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