Account prepared by:  Victor Lyon, United States Fish and Wildlife Service

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SPECIES ACCOUNT

Section 1: Species account outline.

SPECIES: Grasshopper Sparrow (Ammodramus savannarum)

SUBSPECIES STATUS: Western Grasshopper Sparrow (A. s. perpallidus) (Coues).

MANAGEMENT STATUS:

In February of 1999, the California Department of Fish and Game, Natural Heritage Division, Natural Diversity Data Base (NDDB) website (www.dfg.ca.gov/whdab/spanimal.pdf) listed grasshopper sparrows as follows:

As a whole species: "demonstrably secure: commonly found throughout its historic range"; the subspecies A. s. perpallidus as: "restricted range, rare: about 21-100 E.O.’s <viable occurrences>, or 3,000-10,000 individuals, or 10,000-50,000 acres of occupied habitat", the subspecies A. s. perpallidus, in California, as: "endangered, about 6-20 E.O.’s, 1,000-3,000 individuals, 2,000-10,000 acres of occupied habitat".

Grasshopper sparrows are also on the Audubon Society’s Blue List, Partners In Flight’s (PIF) Watch List, and the U. S. Fish and Wildlife Service’s MNBMC (Migratory Non-game Birds of Management Concern) list.

RANGE MAPS (California):

I.  Historical references: Grasshopper sparrows in California favored the coastal zone in the southern part of the state though breeding localities seemed "few and far between" (Pemberton 1917). Records of grasshopper sparrows observed in California prior to 1944 are summarized below in Table 1.

Further information is needed regarding the current breeding distribution of grasshopper sparrows in California.

The data gathered from Breeding Bird Surveys conducted 1982-1996 has been compiled by Sauer et al. (1997) to generate, among other things, mean abundance indices of grasshopper sparrows in California by region. In effect, these indices, shown below in Table 2, represent the number of individuals seen, on average, on fifty three-minute counts on early June mornings in each respective region of California.

Table 2. Mean abundance indices of grasshopper sparrows in California by region from Breeding Bird Surveys, 1982-1996 (Sauer et al., 1997)

II. Time of occurrence and seasonal movements: Data regarding the movements of grasshopper sparrows outside of the breeding season is scarce due to their normally secretive nature (Zeiner et al.1990). Although diurnally active, grasshopper sparrows are easily overlooked as "they seldom fly, preferring to run along the ground between and beneath tufts of grass" (Pemberton 1917). Further, in migration, these sparrows appear to move in small, mixed flocks at night (Vickery 1996).

A. Arrival date on breeding grounds: The first arrivals are the males (Smith 1963) which, depending on latitude, arrive in the Central Valley of California in late February to early March (Collier 1994 in Vickery 1996).

B. Departure dates from breeding grounds: Grasshopper sparrows generally migrate south in August or September (Zeiner et al. 1990).
Spring migration period: The northward migration of grasshopper sparrows through California begins in late February and may last into early May (Collier 1994 and Garrett and Dunn 1981 in Vickery 1996).

C. Fall migration period: Fall migrants on the Farallon Islands have been observed in late July through the first of November, peaking in early October (DeSante and Ainley 1980).

D.  Extent of wintering in California: Grasshopper sparrows are rarely, but regularly, winter residents in California (Zeiner et al. 1990). Christmas Bird Counts (CBCs) in Santa Cruz, San Benito, Monterey, San Luis Obispo, Santa Barbara, Ventura, Kern, Los Angeles, Orange, San Diego, Imperial, Riverside, and San Bernardino counties typically record grasshopper sparrows in very low numbers (averaging one or less bird per CBC route) (Sauer et al. 1995). As they are readily missed in the CBCs because of their very reclusive behavior, Sauer et al. (1995) have expressed that "these limited data are generally insufficient to definitely establish winter population trends."

III. Migration stop-over needs/characteristics:

A. Stop-over period: No information.
B. Habitat use: No information.
C. Routes: Very little information. Known to have visited the Farallon Islands in the late 60’s and early 70’s during fall migration (DeSante and Ainley 1980) (see "Fall migration period" above).

V.  Foraging strategy: Active search. Vickery (1996) states that exposed bare ground is the critical microhabitat type for effective foraging. Bent (1968 in Zeiner et al. 1990) observed that grasshopper sparrows search for prey on the ground, in low foliage within relatively dense grasslands, and sometimes scratch in the litter.

VI. Displays:

A.  Courtship: The male’s low fluttering flight, done silently or with song, may be answered by a female’s trill. Males may then chase females while singing (Ehrlich 1988).

B.  Territorial: The male alternates between displaying a crouched posture where the head is lowered and the wings are fluttered and singing from the highest perch available (Ehrlich 1988).

C. Distraction: When the nest is approached the female will likely slip off the nest without a trace of commotion and run, or rather sneak away, screened by grass tufts only to appear conspicuously some twenty feet away from the nest and then move further off (Smith 1963). After a short fluttering flight, the female feigns injury, spreading her wings and tail (Ehrlich 1988). Meanwhile, the male may chip and circle the nest at a distance (Dixon 1916). Both may then fly in circles around the nest, raising their crest feathers and flicking their wings and tails, or land and bob up and down on their legs and uttering a sharp chi-ip’s or til-lic’s. (Smith 1963).

A.  Typical breeding densities: Grasshopper sparrows nest in semi-colonial groups of 3-12 pairs (Ehrlich 1988). Smith (1963) recorded breeding densities that ranged from 0.12 to 0.74 males per hectare in Pennsylvania. Collier (1994 in Vickery 1996) observed breeding densities of 0.55 males per hectare in California.

B.  Mating system: Grasshopper sparrows are monogamous through the breeding season (Ehrlich 1988).

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

D.  Post-fledging biology of offspring (where do they go and when?): Little information (see "Average territory size" above).

E. Post-breeding social behavior (do they join in mixed species flocks or simply migrate away?): Grasshopper sparrows do not form winter flocks (Ehrlich 1988).

VII.  Clutch size: 2 to 6, most frequently 4 (n=42) (Smith 1963).

VIII.  Incubating sex: The female alone has a brood patch and incubates eggs (Smith 1963, Ehrlich 1988, Harrison 1975). During incubation, the male defends the pair’s territory (Smith 1963).

VIX.  Incubation period: 11 to 13 days (Smith 1963, Ehrlich 1988, Harrison 1975).

X.  Nestling period: The young fledge at 6 to 9 days after hatching, although still unable to fly (Harrison 1975, Hill 1976, Kaspari and O’Leary 1988).

XI..  Development at hatching: Hatchlings are blind and covered with grayish-brown down (Smith 1968).

XII.  Number of broods: Grasshopper sparrows may produce two broods annually, though protracted favorable weather may allow for a third or, in extreme cases in Florida and Jamaica, a fourth brood (Smith 1963, Ehrlich 1988, Vickery 1996).
Who tends the young: After the young hatch, both parents share the responsibilities of tending the hatchlings and seem more concerned over human intrusion into their territory than before (Smith 1963). Kaspari and O’Leary (1988) observed cooperative breeding by non-parental attendants ("defined as birds bringing food to the nest"). Unrelated juveniles and adults from adjacent territories made 9-50% of the provisioning visits to four of twenty-three nests. Parents facilitated visits from non-parental attendants by moving off the nest yet unrelated birds that did not bring food to the nest were vigorously chased away. Kaspari and O’Leary (1988) suggested that non-parental attendants, rare among the population observed, are likely cases of "misdirected parental care".

XIII.  Diet:

A.  Major food items (by season): The diet, composed of invertebrates (primarily grasshoppers) and seeds, varies by season. Spring diet 60% invertebrates, 40% seeds (n=28); summer diet 61% invertebrates, 39% seeds (n=100); fall diet 29% invertebrates, 71% seeds (n=17), no data for winter (Martin et al. 1951 in Vickery 1996). Major taxa in the diet in mixed prairie (Oklahoma) and tallgrass prairie (S. Dakota) included, respectively: Hymenoptera 0 and 2%, Coleoptera 18 and 10%, Orthoptera 36 and 30%, Hemiptera 9 and 1%, Homoptera 0 and 6%, Lepidoptera larvae 20 and 16%, Araenida 4 and 3%, and seeds 14 and 31% (Wiens 1973b). Grasshoppers, primarily of genera Xiphidium, Scudderia, Hippiscus, and Melanopus, formed 37% of the diet from May through August and 23% the rest of the year (Judd 1901 in Smith 1968). Analysis of the stomach contents of eight grasshopper sparrows taken in California included the following seed types: knotweed (Polygonum sp.), campion (Lychnis sp.), oats, and pigweed (Amaranthus sp.) (Martin et al. 1951 in Vickery 1966).

B.  Drinking: Meets water requirement in part from insects in diet (Zeiner et al. 1990). No further data.

XVI. Wintering grounds needs and distribution: See "Extent of wintering in California" above. Grasshopper sparrows winter south of California to northern South America and in the Greater Antilles (Ehrlich 1988). No further information.

BREEDING HABITAT AND NEST SITE CHARACTERISTICS:

I.  Overview of breeding habitat: Originally restricted to extensive natural clearings and sparsely wooded areas (Smith 1963). Occurs in dry, well-drained native and non-native grasslands, especially those with a variety of grasses and tall forbs for foraging and nesting and scattered shrubs for singing perches. Open grasslands where bunch grasses rather than sod types predominate are selected. "Sod-forming grasses provide a dense mat of vegetation that precludes effective foraging, whereas bunch grasses leave openings or gaps that allow the birds freedom to move about. Also, nest placement is usually associated with bunches of grass" (Whitmore 1981). Occurs mainly on hillsides and mesas in California’s coastal districts (Grinnell and Miller 1944, McCaskie et al. 1979, Garrett and Dunn 1981 in Zeiner et al. 1990). Pemberton (1917) observed grasshopper sparrows on steep hills devoid of vegetation, except for grasses, near canyons harboring live oaks and shrub thickets in Ventura County, California. Also recorded in extensive, alkaline, salt-grass meadow in San Diego County (Dixon 1916). Frequents cultivated grasslands which form bunches (e.g. alfalfa, orchard-grass, and red clover) (Smith 1963). Habitat use is negatively correlated with increasing grass height and litter depth (Smith 1963, Herkert 1994a, Herkert 1994b, Deslisle and Savidge 1997, and Wiens 1969, Skinner et al. 1969, Sample 1989, Herkert 1991b in Herkert 1994b,). Whitmore (1979) documented decreases in population densities in correlation "with increases in vegetation density and a concomitant decrease in bare ground". Abandoned alfalfa fields in Iowa when the vegetation exceeded 30 cm in height (Frawley and Best 1991). Known to maintain approximately equal breeding densities in fields with 0-10% shrub cover, but abandon sites whose shrub cover exceeds 35% (Johnston and Odum 1956). Absence of trees more important than presence of native grasses in southern California (Collier 1994 in Vickery 1996). Appears that vegetation structure, rather than composition, is the more important criteria in breeding habitat selection.

II.  Nest site:

A.  Substrate: Nests are built of grasses, forbs, sedges, and other fine materials, occasionally including hair (Harrison 1975, Ehrlich 1988, Zeiner et al. 1990). These are usually woven into the overhanging grasses. Three identical nests in Ventura County, California were made of fine, dry grasses and lacked an appreciable lining (Pemberton 1917). In San Diego County, Dixon (1916) observed a nest of fine, dead weed stalks (wild oat, salt grass, and some other unidentified species) loosely pressed together. No feathers, fur, or other animal matter were incorporated into the nest.

B.  Height of nest: The nest is built by the female (Harrison 1975) at the base of large tufts of grass (Pemberton 1917). The nest is sunken in a slight depression so that the rim is flush with ground level (Ehrlich 1988) and the female’s back is nearly flush with ground while brooding (Dixon 1916). Dome of nest 5-7 cm high (Simmons 1925 in Smith 1968).

C.  Height of plant: No quantitative information.

D.  Nest concealment: Nest well hidden at the base of an overhanging clump of grasses or forbs (Dixon 1916,
Zeiner et al. 1990).

A.  Canopy cover: Grasses and forbs (Ehrlich 1988).

B.  Dominant plant species in canopy: see "Overview of breeding habitat" above.

C.  Average shrub cover: Less than 35% desirable (Johnston and Odum 1956).

D.  Dominant shrub species: see "Overview of breeding habitat" above.

E.  Average forb cover: see "Overview of breeding habitat" above.

F.  Dominant forb species: see "Overview of breeding habitat" above.

G.  Ground cover: see "Overview of breeding habitat" above.

H.  Slope: see "Overview of breeding habitat" above.

I.  Aspect: Nest located on the northern or leeward side of large grass tufts (Pemberton 1917).

J.  Tree DBH: Not applicable.

K.  Snags: No information.

L.  Distance to water: No information.

A.  Elevation: Coastal to 1500 m in San Jacinto mountains (Grinnell and Miller 1944, McCaskie et al. 1979, Garrett and Dunn 1981 in Zeiner et al. 1990). Also found in Santa Monica Mountains (Pemberton 1917).

B.  Fragmentation: Habitat fragmentation clearly has a negative effect on grasshopper sparrows. Nest predation and brood parasitism are higher for nests located near (<45 m) a wooded edge than far (>45 m) from a wooded edge (Johnson and Temple 1990).

C.  Patch size: Despite average territory sizes of less than 1 hectare, grasshopper sparrows rarely (<30%) occur on patches even ten times that size (Herkert 1994a). Grasshopper sparrows are significantly more likely to occur in large grasslands. The estimated area requirement (for which the probability of occurrence equals 50% of its maximum) in Illinois was 30 hectares. Using the same measure, Vickery et al. (1994) found the minimum requirement to be 100 hectares. Minimum area requirements from other studies: <20 ha. in Missouri (Samson 1980 in Vickery et al. 1994), 10-30 ha. in Illinois (Herkert 1991 in Vickery et al. 1994). Differences in minimum area requirements may be explained by the effect of relative population level on the selectivity of individuals, as has been shown for many species of birds (O’Connor 1981 in Vickery et al. 1994).

D.  Disturbance (natural or managed): Though habitat-area had a much greater influence on breeding bird community composition, grasshopper sparrows tended to be more numerous on recently burned prairie areas in Illinois (Herkert 1994b). This is consistent with the characterizations of the habitat preferences (low- to medium-height vegetation) of grasshopper sparrows by other studies (Smith 1963, Wiens 1969, Herkert 1994a, Deslisle and Savidge 1997, and Skinner et al. 1984, Sample 1989, Herkert 1991 in Herkert 1994b). However, a severe, natural wildfire that eliminated sagebrush cover in Montana depressed grasshopper sparrow densities for at least three years on shrubsteppe (Bock and Bock 1987 in Vickery 1996). Grasshopper sparrows frequently breed in managed grasslands such as CRP fields and alfalfa fields (Smith 1963). Instances of grasshopper sparrows utilizing fire-induced grassland glades in Michigan (Walkinshaw 1940 in Vickery 1996), capped landfills (A. L. Jones and PDV unpubl. data in Vickery 1996), and restored surface mines (Allaire 1980, Whitmore 1980, Wray et al. 1982 in Vickery 1996) have been recorded.

E.  Adjacent land use: see above.

F.  Other

SPECIAL FACTORS (factors influencing a species occurrence and viability):

A.  Brood parasitism: Hill (1976) observed that while grasshopper sparrows are "very tolerant" hosts of brown-headed cowbirds (60% of cowbird nestlings fledged, n=5), they suffer a "relatively low" (22.2%, n=18) frequency of parasitism in west-central Kansas. In western Minnesota, brood parasitism occurred more frequently at nests of grassland songbirds located near (<45 m) wooded edges than far (>45 m) from wooded edges (Johnson and Temple 1990). The average number of grasshopper sparrows likely to fledge from a parasitized nest is lower than that for a non-parasitized nest (2.0 versus 2.5 in Hill 1976, Johnson and Temple 1986 in Johnson and Temple 1990). Cowbird parasitism in Hill’s (1976) study area occurred from April 16^th until July 16^th, peaking between April 25^th and July 1^st. In an about-turn, an instance of egg-dumping by a grasshopper sparrow into a savannah sparrow’s nest was recorded in Wisconsin (Wiens 1971). Wiens (1971) cited Hamilton and Orians’ (1965) suggestion that a female whose nest had been destroyed might be more easily able to dump her un-resorbed eggs into the nest of a bird tolerant of her species rather than a highly territorial conspecific.

B.  Dietary: see "Foraging strategy" and "Diet" above.

C.  Sensitivity to human-induced disturbance: Nests are often destroyed by mowing in cultivated grasslands; despite the loss of cover, birds stay (Smith 1963) and then suffer increased losses from predators (Ehrlich 1988). Grasshopper sparrows display an increased sensitivity to human disturbance after hatching occurs (Smith 1963).
Pesticide use: No information specific to grasshopper sparrows.
Predators: Nest predators cited in the literature include: Raccoons (Procyon lotor), Red Fox (Vulpes vulpes), Northern Black Racers (Coluber constrictor constrictor), Blue Jays (Cyanocitta cristata), and Common Crows (Corvus brachyrhynchos) (Johnson and Temple 1990, Wray et. al 1982). Loggerhead Shrikes (Lanius ludovicianus) commonly take grasshopper sparrows as prey in Oklahoma and Florida (Stewart 1990, D. Wolfe [pers. comm.], and T. F. Dean [pers. comm.] in Vickery 1996). Many other species, especially those not dependent upon sight to find nests, are likely to be nest predators. Gottfried (1978 in Wray et. al 1982) concluded, from his analysis of nest predation in old-field habitats, that snakes were the primary predators and aerial predators were responsible for only minor losses.

D.  Exotic species invasion/encroachment:

E.  Other:

A.  Age and sex ratios: No information.
B.  Productivity measure(s): No information.
C.  Survivorship: No information.
D.  Dispersal: No information.

A.  Burning. Grasslands with encroaching shrubs should be burned during late winter.
B.  Deferred grazing. Timing of grazing should be delayed until nesting is completed.
C.  Vegetative reclamation. Reclamation of disturbed sites should be with bunch grasses if grasshopper sparrows are to be encouraged; shrub or tree plantings should be avoided."

ASSOCIATED SPECIES (a list of other species that would benefit from management of the target species): mourning dove (Zenaida macroura), brown-headed cowbird (Molothrus ater), northern harrier (Circus cyaneus), savannah sparrow (Passerculus sandwichensis), vesper sparrow (Pooecetes gramineus), horned lark (Eremophila alpestris), western meadowlark (Sturnella neglecta), killdeer (Charadrius vociferus), indigo bunting (Passerina cyanea), and others (list, in part, from Wray et al. 1992).

MONITORING METHODS AND RESEARCH NEEDS: Managing an area for grasshopper sparrows should, at a minimum, include obtaining seasonal population indices and monitoring vegetative response and nesting activity. Local nesting activity (which varies according to latitude and almost certainly from season to season) should be monitored to time the implementation of managed grazing activities.

Further research is needed on the following topics: 1) habitat types, stopover areas, and routes used during migration, 2) biology and behavior of fledged, immature grasshopper sparrows, 3) demographics, 4) pesticide use, 5) exotic species invasion/encroachment and brood parasitism in CA, 6) minimum patch size in CA (varied from 10-100 hectares in studies in other states), and 7) habitat structure/composition requirements in CA (grasshopper sparrows abandoned alfalfa fields when the vegetation exceeded 30 cm in height and other sites whose shrub cover exceeded 35% in out-of-state studies).
 

SCIENTIFIC REFERENCES:

Delisle, J.M., and J.A. Savidge. 1997. Avian use and vegetation characteristics of Conservation Reserve Program fields. J. Wildl. Manage. 61(2): 318-325.

DeSante, D.F., and D.G. Ainley. 1980. The avifauna of the South Farallon Islands, California. Studies in Avian Biol. No. 4. Cooper Ornithol. Soc., Lawrence, KA. 104 pp.

Dixon, J. 1916. Mexican Ground Dove, Western Grasshopper Sparrow, and California Cuckoo at Escondido, San Diego County, Ca. Condor XVIII, March 1916, pp. 83-84.

Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988. The Birder’s Handbook. Simon and Schuster, New York. 785 pp.

Frawley, B.J. and L.B. Best. 1991. Effects of mowing on breeding bird abundance and species composition in alfalfa fields. Wildl. Soc. Bull. 19:135-142.

Grinnell, J., and A.H. Miller. 1986. The Distribution of the Birds of California. Pacific Coast Avifauna No. 27, publ. 1944, reprinted by Artemisia Press, Lee Vining, CA.

Harrison, H.H. 1975. A field guide to birds’ nests. Houghton Mifflin Co., Boston.

Herkert, J.R. 1994a. The effects of habitat fragmentation on midwestern grassland songbird communities. J. Ecol. Appl. 4: 461-471.

Herkert, J.R. 1994b. Breeding bird communities of midwestern prairie fragments: the effects of prescribed burning and habitat-area. Nat. Areas J. 14: 128-135.

Hill, R.A. 1976. Host-parasite relationships of the Brown-headed Cowbird in a prairie habitat of west-central Kansas. Wilson Bull. 88: 555-565.

Johnson, R.G., and S.A. Temple. 1990. Nest predation and brood parasitism of tallgrass prairie birds. J. Wildl. Manage. 54: 106-111.

Johnston, D.W., and E.P. Odum. 1956. Breeding bird populations in relation to plant succession on the Piedmont of Georgia. Ecology 37: 50-62.

Kaspari, M. 1991. Central place foraging in Grasshopper sparrows: opportunism or optimal foraging in a variable environment? Oikos 60: 307-312.

Kaspari, M., and H. O’Leary. 1988. Non-parental attendants in a north temperate migrant. Auk 105: 792-793.

Pemberton, J.R. 1917. Notes on the Western Grasshopper Sparrow. Condor XIX, Jan. 1917, pp. 24-25.

Sauer, J.R., J.E. Hines, G. Gough, I. Thomas, and B.J. Peterjohn. 1997. The North American Breeding Bird Survey Results and Analysis. Version 96.4. Patuxent Wildlife Research Center, Laurel, MD.

Sauer, J.R., B.G. Peterjohn, S. Schwartz, and J.E. Hines. 1995. The Grassland Bird Home Page. Version 95.0. Patuxent Wildlife Research Center, Laurel, MD.

Smith, R.L. 1963. Some ecological notes on the grasshopper sparrow. Wilson Bull. 75:159-175.

Smith, R.L. 1968. Grasshopper Sparrow. Pp. 725-745 in Life histories of North American cardinals, grosbeaks, buntings, towhees, finches, sparrows, and allies (O.L. Austin, Jr., ed.). Pt. 2. U.S. Natl. Mus. Bull. 237.

Vickery, P.D., M.L. Hunter, Jr., and S.M. Melvin. 1994. Effect of habitat area on the distribution of grassland birds in Maine. Cons. Biol. 8: 1087-1097.

Vickery, P.D. 1996. Grasshopper sparrow (Ammodramus savannarum). In The Birds of North America, No. 239 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists’ Union, Washington, D.C.

Whitmore, R.C. 1981. Structural Characteristics of Grasshopper Sparrow Habitat. J. Wildl. Manage. 45(3): 811-813.

Wiens, J.A. 1971. "Egg-dumping" by the Grasshopper Sparrow in a Savannah Sparrow nest. Auk 88: 185-186.

Wiens, J.A. 1973a. Interterritorial habitat variation in Grasshopper and Savannah sparrows. Ecology 54: 877-884.

Wiens, J.A. 1973b. Pattern and process in grassland songbird communities. Ecol. Monogr. 43: 237-270.

Willett, G. 1910. So. Ca. Breeding Records of the Western Grasshopper Sparrow. Condor XII, Nov. 1910, p. 204.

Williams, L.O. 1937. Additional birds observed at Point Lobos Reserve. Condor XXXIX, Sept. 1937, p. 229.

Wray, T., II, K.A. Strait, and R.C. Whitmore. 1982. Reproductive success of grassland songbirds on areclaimed surface mine in West Virginia. Auk 99: 157-164.

Zeiner, D.C., Laudenslayer, W. F., Mayer, K. E., and White, M., eds. 1990. California’s Wildlife, Volume II, Birds. California Statewide Wildlife Habitat Relationships System. Calif. Dept. Fish and Game, Sacramento, CA.

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