Song Sparrow (Melospiza melodia)
Photo by Eric Preston
Prepared by: Diana Humple (dianahumple@prbo.org) and Geoff Geupel (ggeupel@prbo.org)
PRBO Conservation
Science
4990 Shoreline
Highway
Stinson Beach,
CA 94970
(415) 868-0655
SHORTCUTS
RECOMMENDED CITATION
Humple, D. and G. R. Geupel. 2004. Song Sparrow (Melospiza melodia). In The Riparian Bird Conservation Plan: a strategy for reversing the decline of riparian-associated birds in California. California Partners in Flight. http://www.prbo.org/calpif/htmldocs/riparian_v-2.html
SUBSPECIES STATUS:
Song Sparrows have the greatest number of genetically distinct populations of any bird in North America. The total number of subspecies is much debated, but the most recent study suggests there are perhaps as few as 24 in total (Patten 2001 in Arcese et al. 2002): 11 that breed in California (with some recent debate and modifications to subspecies status), and 8 that are endemic to the state (Shuford 1993, Grinnell and Miller 1944, Roberson and Tenney 1993). Four additional subspecies winter in California (Grinnell and Miller 1944). See Historical References below for complete range information of every subspecies.
MANAGEMENT STATUS: No special status for the species as a whole.
The Channel Island Song Sparrow (M. m. graminea) is a state species of special concern (CDFG and PRBO 2001) and occurs or has occurred on various islands. This subspecies includes two groups formerly classified as their own subspecies, the San Clemente Island Song Sparrow and the Santa Barbara Song Sparrow, both of which are now extinct (Patten 2001 in Collins [in review]).
The three subspecies that inhabit the marshes around the San Francisco Bay area (the Suisun Song Sparrow, M.m. maxillaris; Samuel's Song Sparrow, M.m. samuelis; and the Alameda Song Sparrow, M.m. pusillula) are all state species of special concern in California (CDFG and PRBO 2001).
The Modesto Song Sparrow (M.m. mailliardi) in the Central Valley is also a state species of special concern (CDFG and PRBO 2001), and of all the Song Sparrow subspecies that have this status, is the only one strongly associated with woody riparian habitat.
DISTRIBUTION
Information on historical distribution and abundance, and current distribution (especially breeding). Throughout this text, locations in California will be lumped under the following bioregions: Klamath, Modoc, Sierra, Sacramento Valley, San Joaquin Valley, Bay/Delta, Central Coast, South Coast, Mojave, and Colorado Desert.
HISTORICAL BREEDING DISTRIBUTION
All information in this section is from Grinnell and Miller (1944) except where specified. This section is divided into subspecies. It seemed the most fitting location to present the incredible detail that Grinnell and Miller (1944) themselves presented on all the California subspecies, and in many cases is not outdated. Some recent revisions of subspecies status (including those made since the original version of this species account) are included here.
Subspecies that breed in California:
• Modoc Song Sparrow (M.m. fisherella): Breeds in Great Basin region from Oregon border south along eastern flank of Sierra Nevada through Owens Valley and Shasta Valley south to upper Trinity River system, and in Sacramento drainage to Tehama County. Summer resident in northern interior and eastern sections, and in considerable numbers there throughout year. Partial migration in late September and October accounts for winter visitors southward/westward. In winter additionally occurs south into lower Sacramento and San Joaquin Valleys and on western Mojave Desert, coastal southern Cal, and SF Bay region. Breeds in riparian vegetation, marshes, and lake borders. According to Patten (2001 in Arcese et al. 2002) is included within M. m. montana. In California, primarily the Modoc, Klamath and Sierra bioregions.
• Mendocino Song Sparrow (M.m. cleonensis): Permanent resident. Range: Northwest coastal strip from Del Norte County south through Humboldt County to central Mendocino County, chiefly (if not entirely) within 20 miles of the sea. Klamath Bioregion.
• Modesto Song Sparrow (M.m. mailliardi): permanent resident, central lower basin of Central Valley, from Colusa south to Stanislaus County and east of Suisun Marshes. Fresh-water marshes and riparian thickets. Species of special concern in California (CDFG and PRBO 2001). Primarily the Sacramento Valley Bioregion. Patten (2001 in Arcese et al. 2002) considers this subspecies to be part of the Heerman's Song Sparrow subspecies complex.
• Marin Song Sparrow (M.m. gouldii): permanent resident. Range: central coast districts from interior and southern coastal Mendocino County and Lake County, south to northern shores of San Francisco Bay but exclusive of salt-marsh areas; from coast inland to western Solano and Yolo Counties, west and south to Marin County. Also coastally south of Marin County to the Santa Cruz Mountains area. Former Santa Cruz Song Sparrow (M. m. santaecrucis) is now Marin Song Sparrow in portions of its range (Nolan 1968e, Patten 2001 in Arcese et al. 2002). Bay/Delta Bioregion.
• Heermann's Song Sparrow (M.m. heermanni): permanent resident, southern part of San Joaquin Valley, from Merced to Kern Counties, including along rivers in foothills and lower mountains which drain into it. Numbers have greatly increased in "last 35 years" [written in 1944] due to development of irrigation systems in previously unoccupied parts of its general range: Marsh and riparian habitats. Primarily in the San Joaquin Valley Bioregion. Former Santa Cruz Song Sparrow (M. m. santaecrucis) is now Heermann's Song Sparrow in portions of its range, Marin Song Sparrow in others. According to Patten (2001 in Arcese et al. 2002) this subspecies is inclusive of San Diego (M. m. cooperi) and Modesto (M. m. maillardi) Song Sparrow subspecies.
• San Diego Song Sparrow (M.m. cooperi): permanent resident. Range: valleys of coast ranges from southern Monterey County southward, and Pacific slopes of southern California south to Mexican boundary, eastward across desert divides into Mojave River drainage and streams on east side of San Jacinto Mountains and mountains of San Diego county. Riparian and marshes (primarily fresh water). Central Coast and South Coast Bioregions. Patten (2001 in Arcese et al. 2002) considers this subspecies to be part of the Heerman's Song Sparrow subspecies complex.
• Samuel's Song Sparrow (M.m. samuelis): permanent resident, salt marshes along north side of SF and San Pablo bays, and on south side of San Pablo Bay southwest to San Pablo Point on Richmond headland. Species of special concern in California (CDFG and PRBO 2001). Bay/Delta Bioregion.
• Alameda Song Sparrow (M.m. pusillula): permanent resident, salt marshes bordering south arm of SF Bay, from SF on west south to vicinity of Palo Alto and Alviso, Santa Clara County, and north on east side of Bay. Species of special concern in California (CDFG and PRBO 2001). Bay/Delta Bioregion.
• Suisun Song Sparrow (M.m. maxillaris): permanent resident, marshes surrounding Suisun Bay, from vicinity of confluence of Sac and SJ rivers west to Carquinez Straits. Species of special concern in California (CDFG and PRBO 2001).Bay/Delta Bioregion.
• The Channel Island Song Sparrow (M. m. graminea) is resident on the Channel Islands off of California. This subspecies is considered to include the now extirpated populations on San Clemente and Santa Barbara Islands (Patten 2001 in Collins [in press]), that were formerly considered by Grinnell and Miller (1944) and others to be distinct subspecies (M. m. clementae and M. m. graminea, respectively). On Santa Barbara Island Song Sparrows were still described as an "abundant" permanent resident in 1944; have been extirpated since around 1960 (Garrett and Dunn 1981). Also includes the formerly classified San Miguel Song Sparrow (M.m. micronyx). South Coast Bioregion.
• Desert Song Sparrow (M.m. saltonis): permanent resident, Colorado River Valley and Salton Basin. Patten (2001 in Arcese et al. 2002) considers this subspecies to be part of the M. m. fallax subspecies complex and not diagnosably different. Found in riparian plant associations and marshes. Colorado Desert and Mojave Bioregions.
Wintering subspecies that do not breed within the state of California:
• Mountain Song Sparrow (M.m. montana): winter visitor along eastern border of state (Death Valley, Inyo County, and Colorado R. Valley south to Fort Yuma); migrates north in later March/early April. riparian (Grinnell and Miller 1944). This subspecies breeds in most of the Rocky Mountains (Nolan 1968a).
• Merrill's Song Sparrow (M.m. merrilli): fairly common winter visitant in interior of northern portion of state; chiefly Sacramento Valley, northern San Joaquin Valley, and surrounding foothills (Grinnell and Miller 1944). Breeds in interior of northwestern states (Nolan 1968b).
• Rusty Song Sparrow (M.m. morphna): fairly common winter visitant, chiefly northern half of state from Sierran foothills westward (Grinnell and Miller 1944). Breeds in southwest British Columbia and western Washington and Oregon (Nolan 1968c).
• Yakutat Song
Sparrow (M.m. caurina): rare winter visitant, northwest coastline south
to San Francisco Bay (Grinnell and Miller 1944). Breeds on coast of southeastern
Alaska (Nolan 1968d).
CURRENT BREEDING DISTRIBUTION
Type of method used in determining breeding status (by site and year).
EXPERT OPINION:
Statewide distribution:
Widespread breeder
throughout most of the state except for much of the higher mountains and the
deserts of the east and southeast where the only breeding Song Sparrows are
saltonis (Salton Basin and Colorado River) and cooperi subspecies
(Mojave Basin and east side of San Jacinto Mountains) (Small 1994, Sauer et
al. 2004).
Klamath Bioregion: Common resident and breeder in northwestern part of state (Harris 1991). Modoc and Sierra Bioregion: The Modoc Song Sparrow (M.m fisherella) breeds on the east side of the Cascades-Sierra axis, from the Oregon border south through the Owens Valley. Has possibly colonized the Cottonwood Basin of the White Mountains (Johnson and Cicero 1986 in Small 1994). Sierra Bioregion: Summer resident in riparian habitat of Yosemite area and the East slope of the Sierras (see Elevation section) (Gaines 1988), and are resident in Owen’s Valley (Garrett and Dunn 1981). Sacramento Valley Bioregion: Along the lower reaches of the Sacramento River in California’s Central Valley, the Modesto Song Sparrow is notably absent from almost all riparian habitat, although they are present in wetland areas (PRBO data 1995-1999). South Coast Bioregion: Common permanent resident in riparian thickets and wet brush in portions of southern California; resident locally in lower mountain areas (Garrett and Dunn 1981). In Santa Barbara County the San Diego Song Sparrow (M.m. cooperi) is a permanent resident (Lehman 1994). In Orange County, they are a common permanent resident of marshes, riparian scrub and mesic chaparral along coast to foothills, and also breed in riparian habitat in mountains, where they are locally a fairly common breeder (but are rare in winter) up to 3000 feet (Hamilton and Willick 1996). Colorado Desert and Mojave Bioregions: Desert Song Sparrow (M.m. saltonis) is an uncommon resident in the Salton Basin and Colorado River Valley, where they inhabitat riparian, marshes, and saltcedar. Appear to be declining in region (Garrett and Dunn 1981, Small 1994).
POINT COUNT (singing individual encountered on 2 or more different days of census-at least one week apart):
Klamath Bioregion: Upper Sacramento River (PRBO data 1991-1997); Clear Creek, near Redding (PRBO data 1999-2003); riparian habitat on east slope of Coast Range foothills, at edge of Sacramento Valley Bioregion (PRBO data 1997-1999). Modoc Bioregion: In meadows and riparian areas in Lassen National Forest and Lassen Volcanic National Park (PRBO data 1997-2003); in riparian areas on the east side of Cascades in the Modoc Plateau (PRBO data 2002-2003). Sierra Bioregion: East side of the Sierras in the Owens River and Mono Lake Watersheds (PRBO data 1998-2003). Sacramento Valley Bioregion: Absent in most of the riparian habitat of this region. Found at one site located within 2 miles from the mainstem of the lower Sacramento River, in marshy habitat dominated by tule, cattail, and black willows, near Perkins and Eddy Lakes (Stacy Small pers. comm.). Apparent source population found in marsh in the Butte Sink region (PRBO data 1998-1999). Found in riparian along Cottonwood Creek in the northern portion of the Valley (PRBO data 1999). San Joaquin Valley Bioregion: San Luis National Wildlife Refuge (PRBO data 1995-1997); detected during breeding season at over half of the point count stations censused along the San Joaquin River and its tributaries (Stanislaus, Merced, Tuolomne, and Kings Rivers) (PRBO data 1998-1999); San Joaquin National Wildlife Refuge (PRBO data 2000-2003). Bay/Delta Bioregion: In riparian habitat in Marin County, Song Sparrows were the most abundant of all species (Holmes et al. 1999, PRBO data 1996-2003); Cosumnes River (PRBO data 1995-2003); San Mateo County (PRBO Data 1999); Presidio National Park in San Francisco County (PRBO Data 1999-2003). Central Coast Bioregion: Santa Cruz County (PRBO Data 1999).
MIST NETTING (female with brood patch, female with eggs in oviduct, juvenile with no skull ossification before 1 August):
Klamath Bioregion: Upper Sacramento River (PRBO data 1991-1997); Clear Creek, near Redding (PRBO data 1999-2003); riparian habitat on east slope of Coast Range foothills at edge of Sacramento Valley Bioregion (PRBO data 1997-1999). Modoc Bioregion: Lassen region (PRBO data 1997-2003). Sierra Bioregion: East side of the Sierras (PRBO data 1998-2003). San Joaquin Valley Bioregion: San Luis NWR (PRBO data 1995-1997), Los Banos and O'Neill Forebay Wildlife Areas (CDFG 1996-2003); San Joaquin NWR (USFWS data 2000-2003). Bay/Delta Bioregion: coastal scrub (PRBO 1965-2004) and riparian (PRBO 1995-2003) habitats in coastal Marin County; San Francisco Bay marshes (PRBO data 1996-2003); Cosumnes River (PRBO data 1995-2003). Colorado Desert Bioregion: Salton Sea drainages, Imperial County (PRBO data 1999).
NEST SEARCHING:
Klamath Bioregion: Upper Sacramento River (PRBO data 1993); Clear Creek near Redding (PRBO data 1999-2003); riparian habitat on east slope of Coast Range foothills at edge of Sacramento Valley Bioregion (PRBO data 1997-1999). Modoc Bioregion: Lassen region (PRBO data 1997-1999). Sierra Bioregion: East side of the Sierras (PRBO data 1998-2003); South Fork Kern River Valley at southern end of Sierra Nevada (Larison et al. 1998). San Joaquin Valley Bioregion: San Luis NWR (PRBO data 1995-1997), riparian areas near Fresno (PRBO data 2003), and San Joaquin NWR (2000-2003). Bay/Delta Bioregion: coastal scrub (PRBO 1980-2003) and riparian (PRBO 1996-2003) habitats in coastal Marin County; San Francisco Bay marshes (PRBO data 1996-2004); Cosumnes River (PRBO data 1995-2003).
SPOT MAPPING
Klamath Bioregion: Clear Creek near Redding (PRBO data 1999-2003); riparian habitat on east slope of Coast Range foothills at edge of Sacramento Valley Bioregion (PRBO data 1997-1999). Modoc Bioregion: Lassen region (PRBO data 1997-1999). Sierra Bioregion: East side of the Sierras (PRBO data 1998-2003). San Joaquin Valley Bioregion: San Luis NWR (PRBO data 1995-1997) and riparian areas near Fresno (PRBO data 2003). Bay/Delta Bioregion: coastal scrub (PRBO 1980-2003) and riparian (PRBO 1996-2003) habitats in coastal Marin County; San Francisco Bay marshes (PRBO data 1996-2004); Cosumnes River (PRBO data 1995-2003). Central Coast Bioregion: Santa Cruz County riparian habitat (PRBO data 1999).
AREA SEARCH:
Central Coast Bioregion: Santa Cruz county (PRBO data 1999); east of San Francisco Bay, Alameda and Contra Costa counties (PRBO data 2000-2003). .
BREEDING BIRD ATLAS:
Klamath Bioregion:
Detected in 64%
of all blocks in Humboldt County during the 1995-1999 period when the area was
surveyed (Hunter et al. in prep.). Bay/Delta Bioregion: breed in riparian,
wetland, dense thickets, coastal scrub in fog belt in Sonoma County (Burridge
1995). Breed in coastal scrub, salt, fresh and brackish marshes, riparian, dunes
scrub, and edges of all these habitats in Marin County (Shuford 1993). Central
Coast Bioregion: Most abundant in northern part of Monterey County along
Salinas, Carmel and Pajaro Rivers, and in habitat along the Elkhorn Slough marshes;
generally avoid montane terrain, and scarce in dry foothills, grasslands and
chaparral (Roberson and Tenney 1993). Song Sparrows present along most creeks
surveyed in Santa Cruz County (not present on Cascade Creek, West and East Forks
of Waddell Creek, Fall Creek, Boulder Creek, and King's Creek (in preparation;
Suddjian pers. comm). South Coast Bioregion: common in riparian woodland
and riparian scrub in San Diego County (Unitt 1999).
BBS ROUTE:
Found throughout California during breeding season, but missing from southeastern portion of state. Numbers low on east side of Sierras in southern half of California, as well as in the Sacramento Valley. Most common along coast and in marshes surrounding the San Francisco area bays (Sauer et al. 2004).
ECOLOGYAVERAGE TERRITORY SIZE
See Typical breeding densities below. No other information available.
TIME OF OCCURRENCE AND SEASONAL MOVEMENTS
ARRIVAL DATE ON BREEDING GROUNDS AND ONSET OF BREEDING: Year-round residents in many regions. Earliest dates for breeding occur in salt marshes (Johnston 1954). Klamath Bioregion: At Clear Creek near Redding (PRBO data 1999-2003), earliest first egg of all nests found was 2 April (n=31). At East Park Reservoir (Colusa County Coast Range foothills), earliest first egg was 29 April (n=20). Modoc Bioregion: At Lassen (LNF, LVNP), the earliest first egg of all nests found was 26 April, and the latest date any nest remained active was 7 August (n=43; King and King 2000). Sierra Bioregion: At the eastern Sierra sites combined, earliest first egg was May 11, latest date any nest remained active was 16 August, and mean date of first egg was June 8 (n=80) (Heath et al. 2002). Bay/Delta Bioregion: Year-round resident in Marin County (M.m. gouldii). In 1997 earliest egg laid was March 12 and latest was July 5. This range was longer than for any other riparian breeder monitored at these nest plots, many which were Neotropical migrants (Small and Geupel 1998). Combined with riparian data from GGNRA, the mean data of first egg during the 1997 breeding season was May 3rd (SE=3.0, n=95) (Small and Geupel 1998). San Joaquin Valley Bioregion: At the San Luis NWR, earliest date of clutch completion date was April 4, latest was June 27, and mean was May 17 (n=10, 1995-1997) (Ballard and Geupel 1998). Other regions: in Ohio, two main spring migration flights were a first early migration of males in late February or early March, and a second, main flight of both sexes in mid-March. She also found that age makes a difference in arrival dates, with second-year birds sometimes arriving later (Nice 1964).
DEPARTURE DATE FROM BREEDING GROUNDS: Little information for California. Many populations resident, but some are short-distant migrants. Klamath Bioregion: At Clear Creek near Redding, at least one individual still on breeding territory mid-October (Klamath Bird Observatory and PRBO data 2003). Modoc Bioregion: At relatively high elevations in Lassen (LNF, LVNP), some individuals still on territory through late September, at which point fall monitoring ceased (PRBO data 1998). Other regions: summer females recorded at Ohio study as late as October 16 and males as late as October 31 (Nice 1964).
MIGRATION STOPOVER CHARACTERISTICS
Little information exists on Song Sparrow stopover requirements.
FOOD HABITS
FORAGING STRATEGY
Noted for scratching the ground with its feet to expose invertebrates hidden under surface litter (Roberson and Tenney 1993). Forage primarily on ground, picking food from the ground or litter or at bases of bushes. Also search the mud or shallow water along streams (Shuford 1993).
DIET
Primarily insectivorous during breeding season, and especially in non-breeding season also eats seeds and fruits (see summary in Arcese et al. 2002). Year-round diet consists of 21% animal matter, 79% vegetable matter. Animal prey in the diet rise from a low of 3% in September to over 71% in May. Important animal items include: beetles, caterpillars, bees, ants, wasps, true bugs, flies; chief plant food: weed seed (Beal 1910 in Shuford 1993).
DRINKING
No information available.
BREEDING HABITAT
In California primarily breed in riparian habitat or wetlands, or coastal scrub along the fog belt where the lack of standing or running water is compensated by moisture from fog (Burridge 1995, Roberson and Tenney 1993). Marshall (1948) concludes that their main requirements are:
They are also found in habitats other than riparian. In San Francisco Bay area fresh or brackish marshes, prefer tall rank growth of cattails and bulrushes; in tidal sloughs, found nesting in cordgrass, pickleweed, or gumplant (PRBO data). In coastal Marin County, although found primarily in riparian and coastal scrub habitats, were also found in dune scrub, mixed evergreen hardwood forests (primarily Douglas fir canopy) in areas with thick understory, and in riparian redwood forests (PRBO data 1999, pers. obs.). In noncoastal regions in Marin County Song Sparrows were detected during breeding season (but generally in relatively low numbers) in redwoods, oak woodlands, mixed evergreen hardwood forests, and chaparral; point count stations where they occurred were near water (Holmes et al. 1998).
NEST SITE
VEGETATION SURROUNDING THE NEST
Canopy cover:
Bay/Delta Bioregion: For nests in riparian habitat in coastal Marin County, mean=11.3% (SD=7.44), mode=0, median=10.5, range=0-30%, n=128 nests (PRBO data 1997-1999). In riparian habitat along the Cosumnes River, mean=11.9% (SD=12), mode=0, median=12, range=0-40, n=268 nests (PRBO data 1995-1999). In coastal Marin County riparian habitat, Song Sparrow abundance as detected by point counts was significantly negatively correlated with tree cover and closed canopy cover (p<0.05) (Holmes et al. 1999). In the same region and habitat a positive correlation was found between Song Sparrow nest site selection and number of mid-size (23-28cm dbh) tree stems (p<0.05) (n=218, 95 nest sites and 123 non-use sites) (Small et al. 1998). San Joaquin Valley Bioregion: Analysis of extensive riparian point count and vegetation data in the San Joaquin Valley, correlating presence or absence of Song Sparrows with amount of tree cover within a 50 meter radius of the point, revealed a negative correlation between Song Sparrow presence and amount of tree cover (p=0.001, n=329 points, likelihood ratio test). Mean tree cover at points with Song Sparrows was 17.79% (SE=13.85) and at points without Song Sparrows was 24.40% (SE=16.02). A negative correlation was also found between Song Sparrow presence and the height of the upper canopy (p<0.001, n=324, likelihood ratio test). Mean height of the upper canopy at points with Song Sparrows was 17.79m (SE=8.07) and at points without Song Sparrows was 23.42m (SE=6.74) (PRBO unpublished data 1998).
Dominant plant species in canopy:
Klamath Bioregion:
Although Song Sparrows frequently place their nests in areas dominated by white
alders at Clear Creek, near Redding, a significant negative relationship was
found between nest success and white alder cover and density (p=0.01, pseudo
r2=0.20, suggesting that these areas are not as conducive to successful nesting
(Burnett and Harley 2003). Bay/Delta Bioregion: Nest success was positively
correlated with the number of small red alder trees (8-23mm dbh) (regression
coefficient =0.23, SE=0.16, p=0.03) and total red alder trees of all sizes (regression
coefficient=0.12, SE=0.06, p=0.01) around the nest in riparian habitat in the
Golden Gate National Recreation Area (p=0.01) (Gardali et al. 1998). A positive
correlation was found between Song Sparrow nest success in coastal Marin County
and number of boxelder tree stems/trunks of all sizes present around the nest
(p<0.05 using univariate analysis and p<0.01 using multivariate analysis)
(Small et al. 1998). In other Marin County riparian habitat, Song Sparrow abundance
as detected by point counts was significantly negatively correlated with tree
richness (p<0.05) (Holmes et al. 1999).
Average shrub cover:
Sierra Bioregion: parasitism rates were positively associated with vegetation cover 2-3m above the ground within 5m from the nest, and negatively associated with cover <1m above the nest within 11.3m from the nest (Larison et al. 1998) (see Brood Parasitism section below for more details and discussion). Bay/Delta Bioregion: At Cosumnes, successful nests were associated with lower mean percent shrub cover around the nest and mean blackberry cover around the nests than at depredated nests (p<0.05, n=123). This might be due to nests in woody shrubs providing easy search image for predators during the early stages of the breeding season when the forest floor is flooded, and Song Sparrows are often forced to nest in the tops of blackberry bushes, which are typically the lowest vegetation protruding above flood waters. This may increase the ease with which predators encounter nests. (Haff and DiGaudio 2000). In Marin County riparian habitat, Song Sparrow abundance as detected by point counts were significantly positively associated with shrub cover (p<0.05) (Holmes et al. 1999). A positive correlation was found there between nest site selection and California blackberry cover (p<0.01 using univariate analysis and p<0.001 using multivariate analysis); a negative correlation was found between nest site selection and willow shrub cover (p<0.05) (n=218, 95 nest sites and 123 non-use sites) (Small et al. 1998). In coastal Marin County ungrazed coastal scrub habitat, as coyote bush abundance increased in the nest patch, nest success decreased. Interestingly, as coyote bush abundance increased in grazed coastal scrub, nest success increased. In the same study it was determined that in ungrazed sites, successful nests were located in wider patches than were unsuccessful nests (p<0.05); however this pattern was not found in the grazed sites (Mary Chase pers. comm.). San Joaquin Valley Bioregion: Analysis of extensive riparian point count and vegetation data in the San Joaquin Valley, correlating presence or absence of Song Sparrows with amount of shrub cover within a 50 meter radius of the point, revealed no significant correlation between Song Sparrow presence and amount of shrub cover (p=0.329, n=329 points, likelihood ratio test) (PRBO unpublished data 1998).
Dominant shrub species:
In Marin County
riparian habitat, Song Sparrow abundance as detected by point counts were significantly
positively associated with the height of the low shrub layer (p<0.05) (Holmes
et al. 1999). Other
sites: In arid eastern Oregon along streams, Song Sparrows were most abundant
in continuous mesic shrub associations, uncommon in discontinuous mesic habitat,
and absent from herbaceous xeric habitat associations (Sanders and Edge 1998).
Average forb cover:
Klamath Bioregion: At Clear Creek near Redding, abundance of Song Sparrows appears to be highly correlated with marshy areas immediately surrounding water dominated by sedges, rushes, or other herbaceous plants, as opposed to areas of woody vegetation (Burnett and Harley 2003). San Joaquin Valley Bioregion: Significant correlates between abundance of Song Sparrows as detected on point count censuses in riparian habitat on the San Luis National Wildlife Refuge and the following vegetation variables were found: negative correlation with grass cover (p<0.02), positive correlation with poison hemlock (p<0.01), positive correlation with Hooker's evening primrose (p<0.01), positive correlation with Scirpus species (p<0.01), positive correlation with alkali mallow (p<0.01), positive correlation with gum plant (gum weed) (p<0.05), and positive correlation with western goldenrod (p<0.05). At this site, not only did Song Sparrows nest primarily in herbaceous substrates, but the area within 5 meters of the nest was almost entirely herbaceous as well (Ballard and Geupel 1998). Bay/Delta Bioregion: Song Sparrow abundance detected by point counts within Marin County riparian habitat was significantly positively correlated with herb cover (p<0.01), marsh cover (p=0.001), and herb richness (number of forb/grass species) (p<0.05) (Holmes et al. 1999). Also in coastal Marin County, a positive correlation was found between Song Sparrow nest site selection and forb cover (p<0.05 using univariate analysis, p<0.001 using multivariate analysis) (n=218, 95 nest sites and 123 non-use sites) (Small et al. 1998).
Dominant forb species:
See Average Forb Cover and Nest Substrate sections.
Ground cover:
San Joaquin Valley Bioregion: Mean ground cover breakdown within 5 meters of Song Sparrow nests at San Luis NWR was 71% forb, 29% grass, and 0% shrub. Bay/Delta Bioregion: Nest success was positively correlated with litter depth around the nest in riparian habitat in the Golden Gate National Recreation Area (p=0.01) (Gardali et al. 1998)
Slope:
In riparian habitat in coastal Marin County, mean=8.8º (SD=14.17), mode=0, median=2, range=0-70º, n=128 nests (PRBO data 1997-1999). In riparian habitat along the Cosumnes River, where landscape is quite flat, mean=0.4º (SD=1.1), mode=0, median=0, range=0-15º, n=255 nests (PRBO data 1995-1999).
Aspect:
In riparian habitat in coastal Marin County, mean=175.7º (SD=112.8), n=67 nests that had an aspect (an additional 61 were on completely flat ground) (PRBO data 1997-1999.
Tree DBH:
Nest success was positively correlated with the number of small red alder trees (8-23mm dbh) (regression coefficient =0.23, SE=0.16, p=0.03) and total red alder trees of all sizes (regression coefficient=0.12, SE=0.06, p=0.01) around the nest in riparian habitat in the Golden Gate National Recreation Area (p=0.01) (Gardali et al. 1998).
Snags/logs:
In coastal Marin County, a negative correlation was found between Song Sparrow nest site selection and log cover (p<0.05) (n=218, 95 nest sites and 123 non-use sites) (Small et al. 1998).
Distance to water
Breeds in habitats where there is standing or running water (riparian or marshes) or coastal scrub along the fog belt where this lack of standing or running water is compensated by moisture from fog (Burridge 1995, Roberson and Tenney 1993). Klamath Bioregion: At Clear Creek near Redding, abundance of Song Sparrows appears to be highly correlated with marshy areas immediately surrounding water (Burnett and Harley 2003). San Joaquin Valley Bioregion: Analysis of extensive riparian point count and vegetation data in the San Joaquin Valley, correlating presence or absence of Song Sparrows with amount of running water within a 50 meter radius of the point, revealed a positive correlation between Song Sparrow presence and amount of running water (p=0.02, n=329 points, likelihood ratio test). Mean amount of running water at points with Song Sparrows was 18.68% (SE=16.13) and at points without Song Sparrows was 12.77% (SE=13.78). A positive correlation was also found between presence of Song Sparrows and amount of standing water within a 50 meter radius of the point (p<0.05, n=329, likelihood ratio test); mean amount of standing water at points with Song Sparrows was 4.56% (SE=8.52), and at points without Song Sparrows was 2.11% (SE=6.84) (PRBO unpublished data 1998).
Nest Substrate
Klamath Bioregion: At Clear Creek near Redding, Himalayan blackberry (28%) and rushes (24%) were dominant substrates, followed by cattail (10%), sedge (10%), alder (7%), and grass (7%) (Burnett and Harley 2003). Modoc Bioregion: At Lassen (LNF, LVNP), grasses and sedges were commonly used nesting substrates (38%), followed by willow saplings (31%), spirea (13%), alder (6%) and corn lily (4%) (n=48) (King and King 2000). Sierra Bioregion: In the Eastern Sierra, Song Sparrows were observed nesting in willow, wild rose, and big sagebrush (n=3) (Heath and Ballard 1999b). Bay/Delta Bioregion: At riparian habitat within the Point Reyes National Seashore (PRNS) and Golden Gate National Recreation Area (GGNRA), nesting substrates were primarily California blackberry, with others in hedge nettle, stinging nettle, sedge, coyote bush, salmonberry, Himalayan blackberry, Cape ivy, and grass (Small and Geupel 1998, Gardali et al. 1998). Very few nests were placed in non-native Himalayan blackberry (Small et al. 1998). In coastal scrub habitat at the Palomarin Field Station within PRNS, the two most common nest substrate species was California blackberry and coyote bush, with the remaining few nests in California sagebrush or rushes (Mary Chase, pers. comm.). In the Tall Forest of the Cosumnes Preserve, one of largest remaining valley oak riparian groves in the California's Central Valley (in Sacramento County), there was very little diversity in nesting substrates used by Song Sparrows, with the most common nesting substrate once again was California blackberry (46%), followed by Himalayan blackberry (20%), wild grape (11%) and grasses (5%) (n=84 nests) (DiGaudio and Geupel 1998); at a forest revegation plot nearby, nesting substrate was much more diverse and was primarily in herbs instead of shrubs (DiGaudio and Geupel 1998). San Joaquin Valley Bioregion: In riparian habitat at the San Luis National Wildlife Refuge, the selected nesting substrates were diverse, primarily herbaceous and did not include willows. Breakdown was grasses (19%), poison hemlock (13%), blackberry (13%), and mugwort, dock, gum plant, sunflower, wiregrass, and ox-tongue, all at 7% (n=15). It should be noted that there is little blackberry at these sites compared to sites examined in other regions, which may account for the low percentage of blackberry as a substrate (Ballard and Geupel 1998).
Height of nest
Nests mostly low to the ground, infrequently to 28 feet (Bent 1968). Nice (1964) found that most first nests of the season are located on the ground, almost the only places in her study area in Ohio where there is sufficient cover to conceal the nest that time of year. At all 5 study areas below combined, the mean height of nest was 45cm, SD=39, median=85, range=0-410cm (n=389, all habitat is riparian, PRBO data). Modoc Bioregion: Lassen (LNF, LVNP riparian): mean=28cm, SD=24, median=25, range=0-110 (n=23) (PRBO data 1997-1999). Sierra Bioregion: East Side (riparian): mean=64, SD=33, range=0-110 (n=9) (PRBO data 1998-1999). Bay/Delta Bioregion: At the Cosumnes Preserve (riparian): mean=38cm, SD=32, median=30, range=0-200cm (n=204) (PRBO data 1995-1999). Within Golden Gate National Recreation Area, coastal Marin County (riparian): mean=56, SD=32, median=50, range=0-200 (n=126) (PRBO data 1997-1999). San Joaquin Valley Bioregion: San Luis NWR (riparian): mean=74, SD=111, median=40, range=0-410 (n=14) (PRBO data 1996-1997).
Height of Nest Plant
At all 5 study areas below combined, the mean height of plant combined was 111cm, SD=108, median=95, range=20-1300 (n=396). Modoc Bioregion: Lassen riparian: mean=105, SD=81, median=70, range=20-350 (n=32) (PRBO data 1997-1999). Sierra Bioregion: East Side riparian: mean=152, SD=91, range=40-300 (n=9) (PRBO data 1998-1999). Bay/Delta Bioregion: Cosumnes riparian: mean=100cm, SD=78, median=90, range=20-1030 (n=211) (PRBO data 1995-1999). GGNRA riparian: mean=120, SD=110, median=100, range=21-1008 (n=127) (PRBO data 1997-1999). San Joaquin Valley Bioregion: San Luis riparian: mean=190, SD=87, median=82, range=20-1300 (n=14) (PRBO data 1996-1997).
Plant Species Concealing Nest
NEST TYPE
Open cup.
BREEDING BIOLOGY
TYPICAL BREEDING DENSITIES
Also see focal species population targets table in riparian plan for additional density estimates of Song Sparrows in California. Klamath Bioregion: At Clear Creek near Redding, there were 0.2 to 0.4 territories per hectare at non-restoration riparian sites (Burnett and Harley 2003). Modoc Bioregion: Along Gurnsey Creek riparian habitat (Tehama County) in Lassen National Forest, there were 1.94 territories per hectare in each of the years 1998 and 1998, n=14 each year (King and King 2000). Sierra Bioregion: In riparian habitat along in the eastern Sierra in 1999, number of territories per creek kilometer was determined along 1.65 creek kilometers of Independence Creek (1.2 territories per cr. km) and 4.55 creek kilometers of Birch Creek (0.2 territories per creek km; Heath and Ballard 1999a). Bay/Delta Bioregion: In riparian habitat along Lagunitas Creek in Marin County, the number of Song Sparrow territories per hectare ranged from 5 to 6.7 during the 1998 field season (n=40-44); in riparian habitat along Redwood Creek in Marin County in 1998, territories ranged from 4.4 to 8.1 per hectare (n=62-71; Gardali et al. 1998). Other sites: In wetland habitat on an island in British Columbia, mean density ranged from 1.7 pairs per hectare to 5.6 pairs per hectare (Rogers et al. 1997).
DISPLAYS
Courting male chases female, flutters wings, often sailing and singing; flies among perches with neck outstretched, head and tail held high, wings vibrating (Ehrlich et al. 1988).
MATING SYSTEM
Monogamous; polygyny known to occur (Erlich et al. 1988, Nice 1964).
CLUTCH SIZE
Ranges generally from 3-5 eggs (rarely 1-6) (Arcese et al. 2002). Central Coast Bioregion: mean clutch sizes for different regions were 3.71 in south central coastal region M.m. gouldii (n=143), 3.53 in north central coastal region M.m. gouldii (n=86) (Johnston 1954). Bay/Delta Bioregion: mean clutch sizes were 3.31 in SF Bay salt marsh, M.m. pusilla (n=48), 3.28 in SF Bay salt marsh, M.m. samuelis (n=119) (Johnston 1954). Sierra Bioregion: mean clutch size was 3.99 in Sierra Nevada, M.m. fisherella (n=32) (Johnston 1954). Other sites: mean clutch size in wetland-breeding Song Sparrows on an island in British Columbia was 3.07 and 2.91 at each of two sites (Rogers et al. 1997). Mean clutch size in Ohio was about 4 (Nice 1964).
INCUBATION
Female (Nice 1964).
INCUBATION PERIOD
12-14 days (Erlich et al. 1988), usually 12-13 (Nice 1964).
DEVELOPMENT AT HATCHING
Altricial.
NESTLING PERIOD
9-12 days (Erlich et al. 1988), 11.0+1 days (Sogge and van Riper 1988).
PARENTAL CARE
Female does brooding (Nice 1964) and both parents do feeding (Erlich et al. 1988).
POST-FLEDGING BIOLOGY OF OFFSPRING
By August, Song Sparrow densities at riparian sites near the East Park Reservoir, Colusa County, which supported many breeding Song Sparrows, were down significantly from the breeding season. Nice (1964) found that young birds become independent at the age of 28-30 days, or 16-21 days after fledging).
POST-BREEDING SOCIAL BEHAVIOR
Resident individuals remain territorial year-round (Roberson and Tenney 1993). Juvenile birds flock with other juvenile Song Sparrows (PRBO data, pers. obs.). Nice (1964) found that Song Sparrows flock in cold, snowy weather; these flocks do not necessarily constitute family groups.
DELAYED BREEDING
Bay/Delta Bioregion: birds breed beginning in their second-year (the first breeding season after the one in which they were fledged) (PRBO data). o Other sites: Nice (1964) found that some young males, both residents and summer residents that depart for the winter, establish territories during their first fall, and that females had clutches during their second-year.
NUMBER OF BROODS
Two or three broods, occasionally four (Erlich et al. 1988). In coastal scrub habitat at PRBO's Palomarin Field Station (Bay/Delta Bioregion), where individuals are closely monitored, 11% of the pairs produced no broods, 60% produced just one brood, 28% produced two broods, and 2% produced three broods in 1998 and 1999 (n=47) (Mary Chase pers. comm.). In that region the breeding season is identical in length in riparian habitat.
BROOD PARASITISM
Song Sparrow is a favorite cowbird host throughout most of its range (Nice 1964). Klamath Bioregion: 1 of 5 nests at Clear Creek near Redding were parasitized in 1999, and another pair was observed feeding a BHCO fledgling (Gardali et al. 1999). Sierra Bioregion: In riparian habitat in the South Fork Kern River Valley, parasitism levels were high during a 2-year study. In 1993, 63% of nests were parasitized, and in 1994, 46% were parasitized. They found no consistent differences of paraisitism levels between mature and restored forest, but the study could not adequately assess for such differences due to cowbird removal efforts, cowbird densities, and ratio of cowbird to host species. Habitat structure variables were examined and some relationships were found. Probability of parasitism increased as foliage cover at heights between 2 and 3 m increased, within 5 m of the nest. The presence of such foliage cover may provide cowbirds perches above the nest site, and thus increase their ability to find nests to host their eggs. Another pattern found was that, within 11.3 m of the nest, as cover above the nest at less than a meter in height increased, rate of parasitism decreased. As this pattern was not found when examining for it within 5 m of the nest, this suggests that such dense cover may reduce parasitism rates by preventing cowbirds from observing host activity in the vicinity (but not necessarily directly around) the nest, as well as directly concealing the nest itself. They suggest that dense vegetation may make finding the nest more difficult, and that cowbirds may give up the search before finding the nest (Larison et al. 1998). In the Mono Basin in 2002, nest survival of parasitized Song Sparrow nests was almost half that of non-parasitized nests (0.24 and 0.46, respectively, n=58 and 25) (Heath et al. 2002). Bay/Delta Bioregion: Along Redwood and Lagunitas Creeks in Marin County, 17% of nests were parasitized in 1997 (n=29), and in 12% in 1998 (n=43). Of these, 7% produced Song Sparrow young in 1997, and 7% fledged cowbird young. None failed as a result of parasitism, but the rate of predation was clearly high. All parasitized nests in 1998 were depredated (Gardali et al. 1998). In riparian and coastal scrub nests combined (primarily riparian) in the Point Reyes National Seashore, 7% of the 73 Song Sparrow nests monitored in 1997 were parasitized. Of these nests, 20% were successful in raising Song Sparrow young, and 80% were depredated; none were abandoned due to the parasitism (Small and Geupel 1998). Song Sparrows had relatively low rate of parasitism at Cosumnes (18%) compared to other species (n=62) (DiGaudio and Geupel 1998). San Joaquin Valley Bioregion: 2 of 16 nests (12.5%), at San Luis National Wildlife Refuge were parasitized, 1995-1997 (Ballard and Geupel 1998). Other sites: Cowbird parasitism increased a lot during a 7 year study from 1930 to 1936, which may have been related to the destruction of much of the understory at this site during the 3rd year of the study (Nice 1964). In wetland-breeding Song Sparrows on an island in British Columbia, the very earliest and latest nests were primarily unparasitized, but the breeding season of the 2 species overlapped by over 90%. At one site, 68% of nests were parasitized (n=186); at a second, 60% were parasitized (n=254). 11% of nests at one site and 5% at the second failed as a direct result of parasitism (Rogers et al. 1997).
WINTERING GROUND NEEDS AND DISTRIBUTION
Can be highly territorial even in fall (Nice 1964) and thru winter (Roberson and Tenney 1993). Sierra Bioregion: In Yosemite/E. Slope of Sierra area, still prefer riparian in winter and during migration, but also wander into drier scrub, residential yards, and tall dense herbaceous vegetation (Gaines 1988). Bay/Delta Bioregion: At the Palomarin Field Station, M.m morphna is not an uncommon winter visitor. Multiple individuals have returned to the same site for consecutive years (PRBO mist-netting data). Central Coast Bioregion: Numbers are augmented by individuals from other subspecies during the winter in Monterey county (Roberson and Tenney 1993). South Coast Bioregion: in Santa Barbara County, breeding numbers augmented by additional individuals in fall and winter; but unknown exactly which subspecies are there in the winter (Lehman 1994). Same true for all of southern California, augmented by northern breeding individuals in winter (Garrett and Dunn 1981). In riparian habitat in mountains up to 3000 feet in Orange County where they are locally fairly common breeders, are rare in winter (Willick 1996).
LANDSCAPE FACTORS
ELEVATION
Modoc, Klamath
and Sierra bioregions: Modoc Song Sparrow nests from 90 to 2400 m. Sierra
Bioregion: Yosemite Area and East Slope: on west slope: common summer resident
below 1500 m, uncommon summer resident to 2100 m, rare summer resident and fall
transient to treeline, uncommon resident below 915 m east of crest: common summer
resident below 2400 m, uncommon to 2700 m, rare to treeline in summer and fall;
fairly common winter resident below 2100 m in Mono Basin and uncommon winter
resident below 2300 m elsewhere east of crest (Gaines 1988). Sacramento
Valley Bioregion: Modesto Song Sparrow in Central Valley breeds mostly or
entirely below 60 m elevation (Grinnell and Miller 1944).
South
Coast Bioregion: in Orange County, breeds locally in riparian habitat in
mountains up to 915 m (but is rare there in winter) (Willick 1996). San Diego
Song Sparrow occurs from sea level up to 1500 m (Nolan 1968f).
FRAGMENTATION
Sacramento Valley Bioregion: Efforts may be attempted to decrease the fragmentation of riparian habitat near the Butte Sink in order to connect the source population of Song Sparrows with the Sacramento River. San Joaquin Valley Bioregion: Detected in San Joaquin Valley in some very fragmented riparian habitat (PRBO data 1998). Other sites: In arid eastern Oregon, along streams Song Sparrows were most abundant in continuous mesic shrub associations, uncommon in discontinuous mesic habitat, and absent from herbaceous xeric habitat associations (Sanders and Edge 1998).
DISTURBANCE
Fire:
Not typically a significant factor due to its infrequency in this habitat type. Bay/Delta Bioregion: At riparian nest plots in the Point Reyes National Seashore, Mayfield estimates of nest survivorship was highest at an unburned and ungrazed site (0.54, n=6), followed by one site burned 2 years prior to this study (0.46, n=24), a grazed site (0.12, n=15) and lowest at another site that was also burned 2 years prior (0.08, n=13) (Small and Geupel 1998). At same riparian sites in the Point Reyes National Seashore in west Marin County, mist-netting was conducted following a fire in September 1995 that severely burned the riparian site itself as well as surrounding coastal scrub habitat. Song Sparrow capture rates increased steadily and markedly from year to year during summer and fall months until peaks in 1998, and were reduced in 1999 to numbers lower than the 1998 peaks but generally (most months) still higher than captures in 1996 and 1997. The high number of juvenile birds at this site accounted for such a pattern: overall July capture rates for just hatching-year Song Sparrows were 8.9, 18.9, 73.9, and 23.6 per 100 net hours, for each year respectively. This pattern was nearly as extreme for the other post-breeding dispersal months of August and September as well. At a non-burned (control) riparian site elsewhere in west Marin County where mist-netting took place during the same time period, this pattern did not occur; instead capture rates remained fairly constant between years (PRBO data).
Flooding:
Frequent disturbance in riparian habitat. While having an effect on nesting Song Sparrows during such events, in many riparian areas frequent flooding is critical to the persistence of habitat appropriate for this and other species. Klamath Bioregion: At East Park Reservoir (Colusa County Coast Range foothills), over the course of the season as the water level dropped, Song Sparrows that were restricted initially to the riparian habitat in May dispersed into the smartweed, tule and cattails, perhaps to forage (Zack et al. 1997). Bay/Delta Bioregion: During portions of the breeding season when water is high, Song Sparrows often must nest in the tops of shrubs directly above the water, as these are the only vegetation available at that time. However it leaves them susceptible to high water events that sometimes occur during the breeding season, and at such times many nests can be lost (M. Lynes, pers. comm).
Grazing:
As the water
table drops in some grazed areas and stream banks become cut and incised, the
result is that appropriate woody riparian vegetation declines and Song Sparrows
decline concurrently. Minimal restoration effort, including removal of grazing
and stopping channel incision (restoring the water table) in places that a creek
has incised, appears to be all that is needed in order to allow mountain meadows
to passively restore themselves (Humple and Burnett 2004). Bay/Delta Bioregion:
Analysis of two years of data collected on grazed and ungrazed coastal scrub
plots at PRBO's Palomarin Field Station, Marin County, no relationship was found
between nest success and grazing. However, the average number of nests fledged
per territory per year was higher in the ungrazed site than in the grazed site,
although the results were not quite significant (p=0.07) (Mary Chase pers. comm.).
Sierra Bioregion: At sites within or near the Almanor Ranger District
of the Lassen National Forest where grazing pressure was recently removed, biologists
are already seeing increases in abundances of Song Sparrow as well as other
riparian species (Humple and Burnett 2004). Results from a study that correlated
habitat structure variables with brood parasitism led authors to suggest that
grazing, because of the manner in which it alters plant composition and reduces
herbaceous cover, likely increases parasitism rates directly (Larison et al.
1998).
ADJACENT LAND USE
No information. In the San Joaquin Valley where Song Sparrows are found throughout, almost all riparian habitat is adjacent to either agriculture, developments, or grazed lands.
PESTICIDE
The proximity of much riparian and wetland habitat in the Central Valley to agriculture could make pesticides a problem for this species, but there is no information available on this subject.
PREDATORS
Potential predators at Cosumnes include feral domestic cats, raccoons, skunks, Virginia opossums, rodents such as Norway rats, Western Scrub-jays, and American Crows (DiGaudio and Geupel 1998). A study in riparian habitat at GGNRA showed that 36% of nests had damage to the nest structure (likely preyed upon by larger mammals), and 64% (n=19) were depredated without damage (likely preyed upon by avian predators, snakes, or small mammals)(Gardali et al. 1998). Predators of wetland nests with artificial eggs on an island in British Columbia included mice, shrews, and Marsh Wrens, as well as unidentified large mammals and other birds; other potential avian nest predators at this study were Northwestern Crows, and Bewick’s Wrens (Rogers et al. 1997).
DEMOGRAPHY AND POPULATION TRENDS
DEMOGRAPHICS:
Age and Sex Ratios:
Other sites: sex ratio of breeding Song Sparrows in Ohio was 1.05 males per female in April and 1.19 males per female in June during the first 6 years of the study, 1930-1935; in 1936 however the ratios were 1.5 males per female in April and nearly 1:1 in June. Proportion of males that were second-years in the population ranged from 26 to 55% (Nice 1964).
Productivity measure(s):
Klamath Bioregion: At Clear Creek, near Redding, Mayfield estimates were low at 15% total nest success and 93% daily success (n=26). Predation was the primary cause of failure, although nests were occasionally parasitized by cowbirds (Burnett and Harley 2003). Modoc Bioregion: Song Sparrows determined to have very high productivity within Lassen region: at one site, 100% of nests found were successful in 1998-1999 (n=8), at a second site 70% of all nests found were successful; and annual Mayfield estimates of nest success at these sites were 29.7% and 75.3%, respectively. The difference between these two years may be related to greater predation by Western aquatic garter snakes in 1998, a heavy snow cover year which resulted in the ground remaining saturated and pools persisting late into the breeding season; frequency of garter snake observations was high at this site this year (King and King 2000).
Bay/Delta Bioregion:
Sierra Bioregion: In the Mono Basin in 2002, nest survival of parasitized Song Sparrow nests was almost half that of non-parasitized nests (0.24 and 0.46, respectively, n=58 and 25) (Heath et al. 2002). San Joaquin Valley Bioregion: low nest success in riparian habitat at San Luis National Wildlife Refuge (where several low open-cup nesting species had low proportions of successful nests), 1995-1997, where 11 of 16 nests failed. Mayfield estimate of nest success was 8% (n=14) (Ballard and Geupel 1998).
Other sites:
Survivorship:
Adult survival of this species from 1992-1998 was estimated at 46.5% at 74 northwestern U.S. MAPS stations combined, and at 58.1% at 10 southwestern U.S. stations (DeSante and O'Grady 2000). Bay/Delta Bioregion: Adult survival averaged 45% at the Palomarin Field Station, and independent juvenile survival to their first year was 23% (Halliburton and Mewaldt 1976). Modoc Bioregion: In riparian habitat in the Lassen area, Song Sparrows had an overall survival rate of 56%. At the site within Lassen Volcanic National Park at 6100 feet, females and males had rates of 49% and 57%; at the site within Lassen National Forest at 5000 feet, females and males had nearly identical survival rates at 58% and 59%, respectively (T. Gardali, R. Burnett, and D. Humple, PRBO unpublished data). South Coast Bioregion: On the Channel Islands, adult overwinter survival was 76% for males and 30% for females in the San Miguel Island Song Sparrow (Sogge and van Riper 1988). Other sites: Mean annual survivorship of adult males was 0.62 and 0.72 at each of two wetland sites on an island in British Columbia, where adult female survivorship was 0.17 at one site and 0.57 at the second; during some years in this region extreme cold decreases survival of adults (Rogers et al. 1997). In Ohio, survival of breeding adult males averaged 60% during the first part of the study; during the rest of the study, after much understory had been destroyed, survival dropped to 48, 23, 30 and 20 percent, respectively. Female return rates ranged from 13-44%, but may not reflect survival but movement (Nice 1964). In Ohio study, average aged of males ranged from 2.5 to 2.75 years (before the understory was destroyed). Later in the study (after the destruction of the understory), average age of males was 1.3 years. 3 individuals were known to have reached 7 years of age, and one was at least 7.5 years old.
Dispersal:
Of 26 banded nestling that survived to adulthood in an Ohio study, 22 took up territories from 100 to 1400 m from their birth places (median distance = 280 m). Of 14 females that survived to adulthood, 2 disappeared, and 12 settled from 45 to 1300 m from their birth places (median distance = 270 m) (Nice 1964).
POPULATION TREND
No statewide trends
for 1966-1979, 1980-2003, or 1966-2003 (Sauer et al. 2004). Sierra Bioregion:
supposedly increased on w. slope of Sierra for elusive reasons (Gaines 1988).
Has possibly colonized the Cottonwood Basin of the White Mountains (Johnson
and Cicero 1986 in Small 1994). Bay/Delta Bioregion: No significant trends
found for Song Sparrows during autumns of 1979-1999 in coastal scrub at the
Palomarin Field Station, (Ballard et al. 2003). Sacramento Valley Bioregion:
Notably absent from almost all riparian habitat in the lower Sacramento Valley.
In this region the Modesto Song Sparrow either prefers wetlands or has been
reduced to breeding only in wetland areas, as it cannot be found in strict riparian
habitat and do not occur along the mainstem of the Sacramento River. Some were
found breeding in sparsely vegetated irrigation ditches on the outskirts of
large breeding wetland populations (T. Gardali pers. comm, PRBO data), and others
were detected during the breeding season within 2 miles from the mainstem of
the Sacramento, in marshy habitat dominated by tule, cattails and black willow
(Stacy Small pers. comm). What is interesting and confusing is the abundant
presence of this same subspecies in riparian habitat on the Cosumnes Preserve,
located in the Central Valley and part of the Bay/Delta Bioregion, as well as
riparian habitat in the northern portion of the San Joaquin Valley Bioregion.
Yet they are absent not only from degraded riparian habitat in the Sacramento
Valley, but from seemingly suitable such habitat as well (PRBO data, T. Gardali
pers. comm.). This is all noteworthy when considering the likelihood that they
historically did breed in riparian habitat in the Sacramento Valley (Grinnell
and Miller 1944). San Joaquin Valley Bioregion: Grinnell and Miller (1944)
report increase of Heermann's Song Sparrow in San Joaquin Valley due to development
of irrigation systems in previously arid portions of the area. South Coast/Central
Coast Bioregions: increase of numbers in coastal plain prior to 1944 due
to development of water systems (Nolan 1968f). Colorado Desert and Mojave
Bioregions: Although Grinnell and Miller (1944) said the range of the Desert
Song Sparrow (M.m. saltonis) has "undoubtedly" increased due to irrigation
in the 1910's-1940's, this subspecies appears to be declining in region (Garrett
and Dunn 1981, Small 1994).
MANAGEMENT ISSUES AND OPTIONS
EXOTIC SPECIES INVASION/ENCROACHMENT
No information.
HABITAT LOSS
MANAGEMENT
Larrison et al. (1998) suggest managing for brood parasitism by identifying structural characteristics of the habitat that reduce parasitism (such as increased herbaceous cover, perhaps by reducing grazing in particular) and altering or improving habitat to obtain this structure.
The absence of Song Sparrows in riparian habitat along the lower Sacramento is alarming, considering their presence in similar habitat nearby, and their continued presence in marshy areas in the Valley. Efforts towards the recolonization of this species in riparian habitat in this region are currently necessary. Work at Clear Creek in the northern portion of the valley suggests a high correlation with marshy areas immediately surrounding water (Burnett and Harley 2003), and such an association should be considered when discussing recolonization efforts.
Five subspecies of Song Sparrows in California are state species of special concern. One of these is a riparian-associated species, and all of these, including one which has locally been extirpated from two islands on which it formerly bred, warn us of the potential vulnerability of other Song Sparrow subspecies throughout the state and elsewhere to similar drastic population losses.
Low nest success in many regions may be due to unhealthy structure of the riparian habitat, allowing for heightened levels of parasitism and predation. Restoration efforts must take into account the need of many landbird species for a healthy understory.
Cattle grazing in some regions, such as the riparian meadows of the Sierras and Cascades, causes the water table to drop and stream banks to become cut and incised. This results in loss of appropriate woody riparian vegetation and a concurrent decrease in abundance of Song Sparrow. Minimal restoration effort, including removal of grazing and stopping channel incision (restoring the water table) in places that a creek has incised, appears to be all that is needed in order to allow some mountain meadows to restore themselves.
ASSOCIATED SPECIES
A list of other species that would benefit from management of the target species include: Common Yellowthroat and Spotted Towhee. In riparian habitat in southwestern Utah, Song Sparrows were associated with Indigo Buntings, Abert’s Towhees, Bewick’s Wrens, and Lazuli Buntings (Whitmore 1975).
MONITORING METHODS AND RESEARCH NEEDS
A greater understanding of the apparent decline of the Desert Song Sparrow is needed before this subspecies follows in the footsteps of some of the others in California.
Restoration and subsequent monitoring is needed in riparian habitat of the Sacramento Valley where Song Sparrows breed only locally. Although innovative restoration is underway in some areas, management for this nonmigratory species requires restoration to occur close to source populations (such as Butte Sink).
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Ballard, G., G. R. Geupel, N. Nur, and T. Gardali. 2003. Long-term declines and decadal patterns in population trends of songbirds in western North America, 1979-1999.
Ballard, G. and G.R. Geupel. 1998. Songbird monitoring on the San Luis National Wildlife Refuge 1995-1997. PRBO report to the USFWS.
Beal, F.E.L. 1910. Birds of California in relation to the fruit industry (II). U.S. Dept. Agri. Biol. Surv. Bull. 34.
Bent, A.C. Life histories of North American cardinals, grosbeaks, buntings, towhees, finches, sparrows, and allies (part two). U.S. National Museum Bulletin No. 237.
Burnett, R. D., and J. H. Harley. 2003. Songbird monitoring of the Lower Clear Creek Floodway restoration project: 1999-2003 comprehensive report. A PRBO report.
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