|Aves (Birds): Passeriformes, Emberizidae
Grasshopper sparrow (Ammodramus savannarum)
Potential Occurrence: Nesting Likely to Occur
State: Species of Special Concern
Other: MBTA, G5 S2
The Grasshopper Sparrow is small (11–13 cm, mass 14.5–20 g), flat-headed, and inconspicuous. The head has a dark, blackish crown that is narrowly streaked with buff and divided by a pale buffy-white crown stripe. Lores are orange-yellow, sometimes extending thinly over and behind the eyes. The bill is deep. Nape is greyish, with fine chestnut or reddish brown streaks. The back is streaked with chestnutrust and black, with yellow wing edges that are brightest at the carpal joint. Tail is short and sharp, with rectrices pointed with bare shaft at tip (as is typical of Ammodramus). Breast is buffy and unstreaked, with a whitish lower breast. Juvenile Grasshopper Sparrows have a band of streaks across their breasts (Vickery 1996; Cannings 1995). (From B.C. Ministry of Water, Land and Air Protection 2004)
Occurs across North America and ranges from southern Canada disjunctly south to Ecuador. Of twelve subspecies currently recognized, four breed in North America (Vickery 1996). A. s. perpallidus occurs very patchily from the Pacific coast, including California, east to the Great Plains. Regarded as “rare” and local in Oregon (Gilligan et al. 1994) and endangered in British Columbia (Cannings 1991). Common only in the Great Plains, but numbers even there are declining with loss of habitat, conversion of pasture to row crops, and fire suppression (Vickery 1996). The Grasshopper Sparrow occurs in California primarily as a summer resident from March to September (Garrett and Dunn 1981, McCaskie et al. 1979); the breeding season extends from mid-March to August (Collier 1994). The winter status of this secretive species is obscure, though it is generally considered rare and appears with greatest frequency on the coastal slope of southern California (Grinnell and Miller 1944; 55 winter records for San Diego atlas, Unitt 2004; CBC maps). The Grasshopper Sparrow is at least partly migratory; the occasional birds seen in winter at breeding localities may not be the same individuals there in spring and summer. (From Shuford and Gardali 2008)
Grinnell and Miller (1944) described the Grasshopper Sparrow as a summer resident from Mendocino, Trinity, and Tehama counties south, west of the Cascade–Sierra Nevada axis and southeastern deserts, to San Diego County, from sea level to 4900 ft (1494 m), as in the San Jacinto Mountains. The only suggestion of breeding in the Great Basin is a 13 July 1928 record of a fully fledged young at 4500 ft (1372 m) in Pete’s Valley, Lassen County (Grinnell et al. 1930), which might have represented an extralimital breeding record or evidence of postbreeding dispersal across the mountains. Willett (1912) considered the Grasshopper Sparrow “fairly common” though local on the southern coast of California, but Grinnell and Miller (1944) designated it “sparse and irregularly distributed” overall in the state and noted its semicolonial nature and variable occurrence from year to year. They noted winter occurrence was mainly in the western lowlands, chiefly in southern California, with records extending north to Fresno County and perhaps to the San Francisco Bay region. (From Shuford and Gardali 2008)
Life History & Threats:
The diet of breeding Grasshopper Sparrows in Nebraska consisted of 33% seeds and 67% arthropods, although nestlings were fed entirely on arthropods (Kaspari and Joern 1993). Adults in Nebraska selected acridid grasshoppers (Orthoptera) and adult Coleoptera above all else, followed by Hemiptera species, although Homoptera species were more widely available (Kaspari and Joern 1993). In other locations including Oklahoma and South Dakota, grasshoppers (Orthoptera species) and Lepidopteran larvae made up a large proportion of the adult diet, although seeds still accounted for 14–39% of breeding season diet (Wiens 1973; Vickery 1996). In Wisconsin, nestlings were fed primarily Lepidoptera larvae, with other items including Odonata, Orthoptera, Hemiptera, Diptera larvae, Arachnida, and Oligochaete (Wiens 1969). Concurrent measures of prey availability revealed that adult Grasshopper Sparrows are not opportunistic foragers as suggested by Wiens and Rotenberry (1979) but rather select prey based on size and profitability (Kaspari and Joern 1993). They avoid small prey, and prey with high chitin ratios, and will strip insects of their chitinous exoskeletons to maximize food value for effort (Kaspari and Joern 1993). (From B.C. Ministry of Water, Land and Air Protection 2004)
Males begin territory establishment upon arrival at breeding grounds (Smith 1968). Pairs form immediately after arrival of females at breeding ground, usually 3–5 days after males. Nest building may be initiated immediately, and the female alone builds the nest over 2–3 days. Nests are typically 11–14 cm in diameter, and 5–7 cm in height. Grasshopper Sparrows commonly produce two or more broods in a year, when conditions are favourable. Nests are not reused in subsequent nesting attempts. Clutch size varies from three to six, with second clutches generally smaller, often with two eggs. (From B.C. Ministry of Water, Land and Air Protection 2004)
The female alone incubates the clutch for 11–13 days (Smith 1968). If a female is flushed while incubating, she is likely to feign injury to distract predators (Smith 1963). There is a record of a Grasshopper Sparrow dumping two eggs into a Savannah Sparrow nest (Wiens 1971). The eggs were incubated and hatched although the nestlings were subsequently predated (Wiens 1971). Both males and females feed nestlings (Vickery 1996). Non-parental attendants helped to feed nestlings at 4 of 23 nests in Nebraska between 1981 and 1984, although it did not affect nestling survival (Kaspari and O’Leary 1988). This was most likely misdirected parental care and not kin-based altruism since there was no evidence of site fidelity (Kaspari and O’Leary 1988). (From B.C. Ministry of Water, Land and Air Protection 2004)
Juveniles are well feathered by 9 days when they leave the nest, and plumage is complete by 10–12 days (Smith 1968). Nestlings in Nebraska departed nests at 6–8 days (Kaspari and O’Leary 1988). Both sexes give approximately 4–19 days of post-fledging parental care before females initiate nest construction for the second clutch. Fledglings disperse immediately from the vicinity of the nest, and young of first brood are dispersed by the time second brood is being fed (Vickery 1996). Grasshopper Sparrows breed the first spring after hatching, and presumably every year after (Vickery 1996). Nesting success rates in Missouri Conservation Reserve Program (CRP) fields were 32–63% (McCoy et al. 1999), 30% in Iowa CRP fields (Patterson and Best 1996), and 20% in Minnesota (Johnson and Temple 1990). (From B.C. Ministry of Water, Land and Air Protection 2004)
Grasshopper Sparrows are thought to experience a low level of brood parasitism by Brown-headed Cowbirds (Molothrus ater) (Smith 1968), although parasitism levels vary throughout their range (2– 50%) (Vickery 1996). One of the five nests recorded in British Columbia had a cowbird egg (Cannings et al. 1987). However, in Ontario, only 8% of nests were parasitized by cowbirds (n = 74) (Peck and James 1987). It is possible that the structure and placement of nests keeps them well hidden from cowbirds (Burger et al. 1994). (From B.C. Ministry of Water, Land and Air Protection 2004)
Urbanization is the primary current threat to the Grasshopper Sparrow. Much of its California habitat lies in the path of expanding cities, especially in southern California and the foothills surrounding the Central Valley. The great expansion of vineyards in the Central Valley and inner Coast Ranges (e.g., Merenlender 2000) is likely removing substantial habitat for this species.The effect of conversion from native to non-native grasslands on Grasshopper Sparrows is unknown, but in Oregon Grasshopper Sparrows prefer native bunchgrass (Janes 1983, Holmes and Geupel 1998). In the Santa Monica Mountains of Ventura County, W. Wehtje (pers. comm.) notes the invasion of Harding Grass (Phalaris aquatica) as a threat to Grasshopper Sparrow habitat. (From Shuford and Gardali 2008)
Depending on degree, the effect of grazing can be negative (Saab et al. 1995) or positive. For example, in humid Oklahoma the species was found only in grazed tallgrass prairie, whereas in arid southeastern Arizona it was eliminated by grazing (Bock and Webb 1984). Behle et al. (1985) ascribed the species’ current rarity in Utah to a history of overgrazing. In the Lake Henshaw basin of north-central San Diego County, heavy grazing in combination with pumping out of groundwater confine the Grasshopper Sparrow to a few mesic microhabitats in an area where it would otherwise likely be widespread. Conversely, during the 1990s, the cessation of cattle grazing in Happy Camp Regional Park near Moorpark, Ventura County, led to Coyote Brush (Baccharis pilularis) replacing grass and Grasshopper Sparrows disappearing (W. Wehtje pers. comm.). Fire suppression may also threaten Grasshopper Sparrows if it leads to grassland converting into unsuitable habitats such as dense scrub. (From Shuford and Gardali 2008)
Habitat & Habitat Associations:
In general, however, Grasshopper Sparrows in California prefer short to middle-height, moderately open grasslands with scattered shrubs. Grinnell and Miller (1944) listed a variety of generalized grassland-like habitats, including alfalfa. Dawson (1923) mentioned a nest near Escondido in an alkaline meadow covered with saltgrass (Distichlis). Often the sparrow’s habitat in this area is an ecotone between grassland and sage scrub, so there are scattered shrubs such as California Buckwheat (Eriogonum fasciculatum) or California Sagebrush (Artemisia californica), used by the birds as song perches (pers. obs.). (From Shuford and Gardali 2008)
In some parts of the sparrow’s California range, native bunchgrasses appear to be important habitat components (e.g., San Diego, Unitt 2004), although this is probably not the case in most of the state, given that non-native annuals dominate most grasslands. In Riverside County’s Santa Rosa Plateau Ecological Reserve, the presence of native grasses was less important than the absence of trees (Collier 1994). These sparrows generally are absent from areas with extensive shrub cover, though some shrubbery is tolerated and perhaps preferred (Johnston and Odum 1956, Bock and Bock 1992, Vickery 1996). Patchy bare ground has also been noted as an important habitat component elsewhere (e.g., in Arizona, Bock and Webb 1984; in West Virginia, Whitmore 1981). The Grasshopper Sparrow is more likely to be found in large tracts of habitat than in small ones (Vickery et al. 1994); minimum area requirements are about 100 ha in Maine (Vickery et al. 1994), 30 ha in Illinois (Herkert 1994). (From Shuford and Gardali 2008)
Grasshopper Sparrows forage exclusively on the ground, and require some amount of bare ground for foraging (Whitmore 1981; Vickery 1996). (From B.C. Ministry of Water, Land and Air Protection 2004)
Grass cover is important for concealing nests (Vickery 1996). Grasshopper Sparrow nests are extremely difficult to find, usually hidden at the base of clumps of grass, clover, dead vegetation, alfalfa, or other cover (Smith 1968). In Florida, A. savannarum floridanus often places nests beneath dwarfed live oak (Quercus minima) instead of grass clumps (Delany and Linda 1998). Nests are sunk into depressions, with the rim flush with the ground. Nests are made of dried grass and lined with fine materials including grasses, sedges, and sometimes hair (Vickery 1996). The top is usually arched or domed at the back, giving it an oven-like appearance (Smith 1968). (From B.C. Ministry of Water, Land and Air Protection 2004)
Grasshopper Sparrows typically select moderately open grasslands and prairies with patchy bare ground (Vickery 1996). Grasshopper Sparrows in Wisconsin occurred at the highest densities in habitats with relatively short vegetation (Ribic and Sample 2001). In eastern Washington, Grasshopper Sparrows were positively associated with perennial grasses, which are indicative of native grassland (Vander Haegan et al. 2000). Soil type (loamy, shallow, or sandy) and range condition (good, fair, or poor) had a significant interaction when used to describe abundance of this species. Grasshopper Sparrows were most abundant in sites that had loamy soil with fair range, or shallow soil with poor range (Vander Haegan et al. 2000). (From B.C. Ministry of Water, Land and Air Protection 2004)
The positive association of Grasshopper Sparrow with cheatgrass, a weedy annual grass, and pasture sage indicates that this species tolerates some level of disturbance, and habitat selection may not be affected by invasion of exotic species (Paczek 2001). Grasshopper Sparrows may respond more to plant structure than floristics, as they were more abundant in areas with abundant Eurasian weeds, relative to native plants in Manitoba, Illinois, and Colorado (Wilson and Belcher 1989; Haire et al. 2000; Walk and Warner 2000). Presence of weeds could indicate habitats that are rich in prey. For example, in Arizona, grasshoppers (Orthoptera) prefer rangelands dominated by weedy herbs rather than wellgrassed ranges (Nerney 1958); in Oklahoma, Orthoptera, particularly acridids, increased in moderate to heavily grazed grassland (Smith 1940)… Song perches in general are important for Grasshopper Sparrows, which sing most often from fixed perches such as shrubs, flower stems, and fence posts, and occasionally from the ground, usually in the periphery of their territories (Vickery 1996). (From B.C. Ministry of Water, Land and Air Protection 2004)
Conceptual Basis for GIS Model Development: Potential foraging and nesting habitat was mapped for the Grasshopper Sparrow in the Study Area as grasslands.
Potential Occurrence in the Galbreath Wildlands Preserve: Protection status for this species applies to nesting individuals.
Habitat: Grasshopper sparrows nest in open grasslands. Nesting habitat in the Preserve is not very abundant but is likely moderate to good in quality (Figure 84). Preserve grasslands, which contain both non-native and native grasses and forbs, have not been grazed since 2000 and provide undisturbed areas for nesting. Adjacent properties, especially areas north of the Preserve, have greater availability of grasslands and agricultural fields preferred by this species.
Documented Occurrences in the Galbreath Wildlands Preserve: This species has not been documented on the Preserve. To our knowledge no surveys have been conducted.
Nearest Occurrence to the Galbreath Wildlands Preserve: This species has been reported to occur in the Hopland USGS quad east of the Preserve, and is widespread in California.
Summary: Nesting Grasshopper Sparrows are “Likely to Occur” in the Preserve due to the occurrence of quality nesting habitat.
B.C. Ministry of Water, Land and Air Protection. 2004. [Grasshopper Sparrow (Ammodramus savannarum)] in Accounts and Measures for Managing Identified Wildlife – Accounts V. 2004. B.C. Ministry of Water, Land and Air Protection, Victoria, B.C. . 2010 September 29.
Hofmann G. Grasshopper Sparrow Photograph. Smithsonian National Zoological Park – Migratory Bird Center. . 2010 September 29.
Shuford, W. D., and Gardali, T., editors. 2008. California Bird Species of Special Concern: A ranked assessment of species, subspecies, and distinct populations of birds of immediate conservation concern in California. Studies of Western Birds 1. Western Field Ornithologists, Camarillo, California, and California Department of Fish and Game, Sacramento.
Species Account Description: Neal Ramus & Emily Harvey