California Partners in Flight Coastal Scrub and Chaparral Bird Conservation Plan
Sage Sparrow (Amphispiza belli)
Photo by James Gallagher, Sea and Sage Audubon
Prepared by: Mary K. Chase
PRBO Conservation Science
Barbara A. Carlson
University of California Natural Reserve System
Chase, M.K. and B.A. Carlson. 2002. Sage Sparrow (Amphispiza
belli). In The Coastal Scrub and Chaparral Bird Conservation Plan:
a strategy for protecting and managing coastal scrub and chaparral habitats
and associated birds in California. California Partners in Flight. http://www.prbo.org/calpif/htmldocs/scrub.html
action plan summary
Five subspecies are currently recognized (belli, clementeae, cinerea, canescens, and nevadensis), although the clementeae subspecies may be more properly grouped with belli (Martin and Carlson 1998, Patton and Unitt 2002). Four of the five subspecies occur in California, but only two (belli and canescens) occur in the area covered by the Chaparral and Coastal Scrub BCP. This species account will focus on the belli and canescens subspecies.
The belli subspecies (Bell's Sage Sparrow) has been listed as a Species of Special Concern in California. The San Clemente Island subspecies (A.b. clementeae), was listed as Threatened by the U.S. Fish and Wildlife Service in 1977.
Formerly known as the Bell Sparrow, the belli subspecies was described as a "common resident of the Upper Sonoran zone west of the desert divides" where it "adheres closely to the chamisal (Adensostoma fasciculatum) association"(Grinnell 1915). Occurred in the southern coastal region from San Diego to Santa Clara and Contra Costa counties and locally in Marin and Sonoma counties, along western rim of Sacramento Valley and western foothills of Sierra Nevada (Grinnell 1915). See also Grinnell and Miller (1944). A. b. canescens was reported in sagebrush belt of mountains surrounding the south end of the San Joaquin Valley, west rim of Owens Valley and near Owens lake, near Walker Pass, near Bakersfield and McKittrick, on Carrizo Plain, south to east slope of San Bernardino Mountains, and north to the west side of Tulare Lake. Also reported in late summer and winter in other parts of interior southern CA (Grinnell 1915).
CURRENT BREEDING DISTRIBUTION:
California distribution described in Small (1994). Distribution in southern CA described in Garrett and Dunn 1981; centers of abundance were western Riverside County and in the vicinity of El Cajon, San Diego County. Fairly common to common resident in semidesert scrub in eastern Santa Barbara County (A. b. canescens) and very uncommon and rare residents in coastal areas of this county (Lehman 1994). Patchy distribution in Monterey County in chamise chaparral but exact extent unknown (Roberson 1985). Small (1994) states A.b. belli to be irregular at northern edge of range in Trinity and Shasta counties, and describes an isolated pocket resident in western Sierra Nevada foothills.
Breeding Bird Atlases:
San Diego County - "Our results so far reveal the Sage Sparrow to be most widespread in south-central San Diego County, where an extensive plateau is still covered with vast tracts of chamise and redshanks. Toward the northwest, where the chaparral is often denser and more diverse, the distribution becomes patchier. The most extensive population remaining near the coast is that on Marine Corps Air Station Miramar, where the Sage Sparrow lives among the vernal pools ..no records of the Sage Sparrow from isolated canyons enclosed within the city of San Diego." (http://www.sdnhm.org/research/birdatlas/).
Contra Costa County - Confirmed breeding in six atlas blocks and probable breeding in one block, all in vicinity of Mt. Diablo, Contra Costa County, (http://www.flyingemu.com/ccosta/sgsp.html).
Marin County - Described as a rare resident of relatively dry chaparral dominated by chamise (Adenostoma fasciculatum). " all breeding season sightings were from the Carson Ridge/Pine Mountain area". Breeding confirmed in one block (Shuford 1993).
Sonoma County - Uncommon and distributed locally in eastern portions of the county. Breeding confirmed in 2 blocks (Burridge 1995).
Within the area covered by this Bird Conservation Plan, BBS distribution map shows three areas where Sage Sparrows reach their highest abundance. Areas of higher abundance also occur in the Mohave bioregion of California and in the Great Basin. Map and counts for each BBS route can be found at http://www.mbr-pwrc.usgs.gov/bbs/
AVERAGE TERRITORY SIZE:
Highly variable. For A. b. belli, territories in San Diego and Riverside counties varied from 0.75 to 5.7 hectares (Lovio 1993, 1995, BAC pers. comm.).
TIME AND OCCURRENCE OF SEASONAL MOVEMENTS:
A. b. belli is generally non-migratory, although northernmost CA populations are reported to be migratory and other populations move down-slope to lower elevations in winter (Martin and Carlson 1998). A. b. canescens believed to migrate southward in winter from northern portions of range, and moves down-slope into deserts in winter in southern CA.
EXTENT OF WINTERING IN CA:
A. b. belli probably winters primarily in CA. Some A. b. canescens
winter in CA but little is known about extent.
Ground-foraging omnivore during breeding season, ground gleaning granivore during non-breeding season (Martin and Carlson 1998).
Breeding season: adult and larval insects, spiders, seeds, small fruits, and succulent vegetation. Fall, winter, and early spring: small seeds, plant material, insects when available (Martin and Carlson 1998).
Drinks occasionally but obtains most of water through diet (Martin and Carlson 1998).
BREEDING HABITAT:Generally "prefers semi-open habitats with evenly spaced shrubs 1-2 m high" (Martin and Carlson 1998). A .b. belli: dry chaparral and coastal sage scrub; chamise chaparral in northern part of range and in coastal San Diego County (Bolger et al. 1997); big sagebrush at higher elevations in southern CA mountains. Less common in tall, dense, old chaparral. A. b. canescens: low desert scrub of saltbush, bitterbrush, big sagebrush and shadscale, and some creosote bush-goldenhead desert scrub (Martin and Carlson 1998). A. b. nevadensis occurrence is associated with sagebrush cover (Knick and Rotenberry 1995).
A .b. belli: diverse shrub species including: brittlebush, black sage, California buckwheat, California sagebrush, bush mallow, chamise, white sage, valley cholla, ceonothus, willow; bunchgrasses used as well. A. b. canescens: saltbush and rabbitbrush. Occasionally nest on ground.
HEIGHT OF NEST:
Mean nest height for belli: 42.3 cm ± 18.1 SD (range 22-79, n=19). No data for canescens.
HEIGHT OF PLANT:
Shrub height and structure believed to be more important to nest site choice than species; prefer taller shrubs with larger canopies. Mean nest shrub height for belli: 105.7 cm ± 22.3 SD (range 62-155, n=21). No data for canescens.
No quantitative data, but nest are placed in densest part of nest site vegetation.
VEGETATION SURROUNDING THE NEST:
AVERAGE SHRUB COVER:
No quantitative data, but where shrub cover is a sparse, nests are found in denser clumps of shrubs. In one study, A. b. belli chose nest sites with taller vegetation within 10 m than was present at random sites (Misenhelter and Rotenberry 2000).
DOMINANT SHRUB SPECIES:
No quantitative data; varies according to habitat. In one study, A. b. belli chose nest sites with more cover from California sagebrush and brittlebush within 10 m than in random sites (Misenhelter and Rotenberry 2000). In the same study, successful nest sites had higher cover of brittlebush and higher plant species diversity within 10 m than did sites of unsuccessful nests.
In one study, A. b. belli chose nest sites with a higher degree of bare ground within 10 m than at random sites (Misenhelter and Rotenberry 2000).
Nest typically placed away from southwest side of shrubs, probably to avoid
wind or sun exposure (Martin and Carlson 1998).
TYPICAL BREEDING DENSITIES:
A. b. canescens: 8.3/km2 in creosote bush-goldenhead scrub in Fremont Valley, Kern Co. and 47/km2 in saltbrush scrub in Cuddleback Lake, San Bernardino Co (Landry 1978a, 1978b). A. b. belli: 94-111/km2 near Perris, Riverside Co. (Carlson 1983). Above densities obtained using BBC method. In central Oregon, Sage Sparrow density averaged 65/km2 between 1976-1980 (Rotenberry and Wiens 1989).
Sings from perches to establish territory.
Mean for belli: 3.54 ± 0.60 SD (range 2-5, n=147). Mean for canescens: 3.62 ± 0.86 SD (range 2-6, n=41) (Martin and Carlson 1998).
Female predominately, although male rarely observed incubating when female leaves nest (Martin and Carlson 1998).
10-16 days from completion of clutch (Martin and Carlson 1998).
DEVELOPMENT AT HATCHING:
Altricial, naked, blind, uncoordinated.
9-10 days (Martin and Carlson 1998).
Both parents feed young.
POST FLEDGING BIOLOGY OF OFFSPRING:
No information beyond parental care stage. Immediately post-fledging, young birds perch low in shrubs and sometimes give begging calls as both parents feed young.
POST BREEDING SOCIAL BEHAVIOR:
Little information for belli and canescens. In winter, belli seen moving in small mixed species flocks with other sparrow species (BAC). A. b. navadensis: juveniles form flocks after fledging and are joined by adults after breeding ends and before migration begins.
NUMBER OF BROODS:
Few data for belli and canescens. A. b. clemente frequently double or triple broods, most nevadensis produce 2 broods per year (Martin and Carlson 1998).
Nest have been parasitized by Brown-headed Cowbirds (Molothrus ater) in Idaho and California, especially in disturbed areas. Both abandonment and the raising of cowbird young have been observed (Martin and Carlson 1998).
Little quantitative information. The lowest known point for A.b. belli on the east edge of the Sage Sparrow's range in San Diego County is at 2050 feet elevation (San Diego County Bird Atlas).
Occurrence of A. b. belli is reduced near edges with human development (Bolger et al. 1997). No records of A. b. belli from isolated canyons enclosed within the city of San Diego (San Diego County Bird Atlas, Soulé et al. 1988, Crooks et al. 2001). High predation rates observed in one habitat fragment in southern California (79.9%; Misenhelter and Rotenberry 2000). Knick and Rotenberry (1995) found that Sage Sparrows were less likely to occur in fragmented shrubsteppe habitats in Idaho. Also, landscape scale variables were more important predictors of Sage Sparrow presence than local habitat characteristics. They concluded that "the fragmentation of shrubsteppe habitats by wildfire, shrub die-off, or human-caused disturbance appears to significantly affect obligate species, such as Sage Sparrows" (Knick and Rotenberry 1995).
Presence of A. b. nevadensis positively related to shrub patch size (Knick and Rotenberry 1995).
DISTURBANCE (natural or managed):
Disturbances that reduce shrub cover, such as frequent fire, mechanical disruption, livestock grazing, and off-highway vehicle use appear to have negative effects on Sage Sparrows, although there may often be a time-lag between the disturbance and any effects due to site-fidelity (Wiens et al. 1986). Disturbances in costal scrub habitats can lead to a change from shrubland to fields of exotic grasses and annual forbs; the latter is avoided by Sage Sparrows (A. b. belli; Misenhelter and Rotenberry 2000). In both shrubsteppe and coastal scrub, the invasion of exotic weeds can cause increased fire frequency, complete loss of shrub cover, and reductions in Sage Sparrow populations. On the other hand, long-term fire suppression in California chaparral may allow shrubs to grow higher and thicker than what is preferred by Sage Sparrows (Martin and Carlson 1998). A. b. belli may prefer recently burned chaparral because it has a low, open shrub structure (Lovio 1999). Disturbance by domestic grazing animals can also reduce habitat and Sage Sparrow numbers, as happened dramatically on San Clemente Island (Martin and Carlson 1998). Habitat disturbance may also promote nest parasitism. In a desert scrub habitat protected from grazing and off-highway vehicle use by fencing, Sage Sparrows were found to be 163-222% more abundant than outside the fencing (Brooks 1999).
ADJACENT LAND USE:
Reduced abundance near urban edges.
Like other open cut nesters, Sage Sparrows are extremely vulnerable to nest predation. Research suggests that nest predation can strongly reduce reproductive success and threaten population persistence (Reynolds 1981, Rotenberry and Wiens 1989, Misenhelter and Rotenberry 2000). Reynolds (1981) reported that Loggerhead Shrikes depredated nests. Snakes and ground squirrels have also been implicated as nest predators (Rotenberry and Wiens 1989). Anything that increases predation pressures (introduced or human-subsidized predators, habitat degradation) is potential a threat to Sage Sparrow long-term viability.
EXOTIC SPECIES INVASION/ENCROACHMENT:
In both shrubsteppe and coastal scrub habitats, the invasion of exotic weeds can cause increased fire frequency, complete loss of shrub cover, and reductions in Sage Sparrow populations (Martin and Carlson 1998, Misenhelter and Rotenberry 2000).
VULNERABILITY TO ECOLOGICAL TRAPS:
Sage Sparrows "selecting habitat in more preferred habitat experienced a higher likelihood of nest failure than did those in less preferred habitat" (Misenhelter and Rotenberry 2000). Therefore some populations of Sage Sparrows may occur in areas that are "ecological traps," and thus these populations may not be viable in the long run.
DEMOGRAPHY AND POPULATION TRENDS:
AGE AND SEX RATIOS:
For A. b. clementeae, 2.5 fledglings per nest ± 0.87 SD, range 1-4, n = 20; (Willey 1990). For A. b. nevadensis, 1.3 fledglings per nest with eggs ± 1.3 SD, range 0-3, n = 15; (Reynolds 1981). Productivity in shrubsteppe habitats is higher in years with higher annual rainfall (Rotenberry and Wiens 1991).
Few data; BAC observed three color-banded young which had moved 800-900 m from their natal nest site by the following spring, and ten hatch-year birds which moved 75-600 meters from their point of capture (Martin and Carlson 1998).
In California, BBS analysis of 52 routes shows no significant trend between 1966 and 2000. However, for individual regions in California, there is too little BBS data available (4-12 routes per region) to reliably estimate trends (http://www.mbr-pwrc.usgs.gov/bbs/).
FIRE AND EXOTIC VEGETATION:
Fire frequency and the invasion of exotic vegetation, especially grasses and annual forbs, interact to pose serious threats to Sage Sparrows in coastal scrub habitat. In much of coastal southern California, where these exotic plants are well-established and where the irreversible conversion of shrublands to grasslands is likely, fire frequency and burn size should be kept low. Where possible, flammable exotics should be removed or reduced in shrubland habitats. However, in chaparral habitats, where re-growth of shrubs following fire is common, prescribed fire may benefit Sage Sparrows.
Sage Sparrows seem to be especially sensitive to fragmentation and development at the landscape scale. The fragmentation of Sage Sparrow habitat is a serious threat in California, due to the overlap between the Sage Sparrow's distribution and areas of expanding human development.
Nest predation may be a serious factor in the declines of Sage Sparows in California. Therefore, predation should be minimized by managing for local and landscape habitat characteristics that are associated with high nest success, and possibly by reducing the abundance of non-native predators.
Greater Roadrunner, Canyon Wren, Rock Wren, Rufus-crowned Sparrow, San Diego pocket mouse (Chase et al. 2000).
MONITORING METHODS AND RESEARCH NEEDS:
Trend monitoring: The BBS method does not monitor Sage Sparrows well in the areas of California where they are most likely to be declining due to habitat loss, fragmentation, and degradation. Off-road monitoring methods should be applied in coastal scrub and chaparral habitats in coastal California. Monitoring plans for NCCP and MSHCP efforts in southern California should include the monitoring of Sage Sparrows.
Demographic monitoring and research: Nest success and the factors that influence it should be monitored directly (through nest monitoring) in replicate sites to evaluate management options. Basic data on survivorship is needed and could be obtained from constant-effort mist-netting or color-band re-sighting. More basic information is needed on other aspects of productivity such as number of nesting attempts and post-fledging and juvenile survivorship. Study of whether Sage Sparrow exhibit metapopulation or source-sink dynamics would be valuable.
Mechanisms of landscape effects: Study of the mechanisms responsible for the reduced incidence of Sage Sparrows near edges and in areas of fragmented habitat is needed. In other words, is the negative association with edges due mainly to habitat selection (the avoidance of edges by individual birds) or due to reduced population growth rates near edges?
Optimal fire frequency: The association between Sage Sparrow occurrence/abundance and fire frequency should be studied to determine what the optimal fire frequency is for maintaining suitable habitat in several bioregions.
ACTION PLAN SUMMARY
SPECIES: Sage Sparrow (Amphispiza belli)
Two subspecies of Sage Sparrows occur in the California shrublands covered by this plan. The Bell's Sage Sparrow (A. b. belli) is a characteristic chaparral and coastal sage scrub bird found mainly in drier, more inland areas of the Coast Ranges and southern California. The canescens subspecies is found further inland in even drier, desert scrub habitats. Breeding Bird survey data from throughout the West indicate declining Sage Sparrow populations, but the data from California alone are insufficient to assess local trends. Given the amount of loss of habitat in coastal California, its distribution in coastal scrub habitat has probably been reduced. The Bell's Sage Sparrow has been listed as a Species of Special Concern in California.
HABITAT NEEDS and CONCERNS:
Sage Sparrows require extensive, semi-open habitats with evenly spaced shrubs 1-2 meters high. Sage Sparrows will benefit from intermediate fire frequencies. Too frequent fires in some shrubland habitats can convert shrubland habitat to grassland and has probably contributed to the decline in Sage Sparrows throughout the western U.S. On the other hand, long-term fire suppression in chaparral allows taller, thicker chaparral to develop, probably reducing Sage Sparrow habitat in California. Other disturbances that eliminate shrubby vegetation, such as those used in some parts of the west to increase livestock forage, should also be avoided. Sage Sparrows in coastal shrublands, as well as in the Great Basin, are highly sensitive to habitat fragmentation, occurring less often in small patches and near developed edges. Thus, large areas of suitable habitat should be preserved to benefit Sage Sparrow populations. Low productivity due to nest predation in fragmented habitats is a cause for concern.
· Maintain current distribution.
· Identify healthy breeding populations.
· Increase area of habitat managed for Sage Sparrows.
· Guide conservation planning efforts to benefit Sage Sparrows.
· Improve trend and demographic monitoring efforts.
· Gather new information on the effects of management practices and habitat fragmentation on Sage Sparrow populations.
Habitat protection recommendations:
Habitat preservation for the Bells' Sage Sparrow should focus on inland coastal sage scrub associations and chaparral that contains chamise. The habitat and area requirements of Sage Sparrows should be addressed in multi-species conservation planning efforts (NCCPs and MSHCPs) throughout their range.
Management and restoration recommendations:
Manage fire frequency and other disturbances to maintain a semi-open shrub structure in coastal scrub and chaparral.
Monitoring and Research Needs:
As is true of many coastal shrubland bird species, Sage Sparrows are not well monitored by Breeding Bird Survey counts. Given their sensitivity to fragmentation and habitat degradation, monitoring to determine population trends and demographics should be a high priority. Because Sage Sparrows may be attracted to areas where they experience low reproductive success (i.e., "ecological traps"), research into the determinants of reproductive success and habitat quality is especially needed. Studies to determine optimal fire frequencies in various habitats, and to understand the mechanisms by which fragmentation influences Sage Sparrows are needed.
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