Restoration Potential: Plant fields with mixture of forbs and short and tall grasses (Jones and Vickery 1997).
Preserve Selection and Design Considerations: May occupy small (< 5 ha) areas of suitable habitat (Potter 1972). However, Jones and Vickery (1997) suggest that minimum grassland size is 20-40 acres and Herkert et al. (1993), based on data from Illinois, categorized the species as highly sensitive to habitat fragmentation. Species with a high area sensitivity are generally restricted to nesting in large, contiguous habitats and rarely nest in small habitat fragments. In New York, density was positively correlated with field size (Bollinger 1988, 1995), whereas in Saskatchewan, occurrence was negatively associated with area (SWCC 1997). In Illinois, Herkert (1991) found no sparrows on grassland tracts < 10 ha and noted that they were significantly more likely to occur on large than small grasslands. Incidence increased with area and reached 50 percent at about 10 ha in Maine (Vickery et al. 1994) and 40 ha in Illinois (Herkert 1994).
In Saskatchewan, 700-1,600 ha may be required to halve brood parasitism (SWCC 1997). In Minnesota tallgrass prairie, abundance was higher, and nest depredation and cowbird brood parasitism rates lower, as distance to wooded edges increased; nest depredation rates were lower on large (130-486 ha) than small (16-32 ha) grassland fragments (Johnson and Temple 1986, 1990).
Management Requirements: BURNING: In Minnesota, Wisconsin, and South Dakota, higher nest densities were found in unburned (for > 12 months) than burned grasslands (Tester and Marshall 1961, Martin 1967, Halvorsen and Anderson 1983, Huber and Steuter 1984). Halvorsen and Anderson (1983) attributed the difference in nesting densities between burned and unburned areas to the lack of litter on burned areas required for nesting. In Minnesota, nesting was significantly correlated with litter cover and litter depth, and may require > 2 years of litter accumulation postfire before using a grassland for nesting (Tester and Marshall 1961). In North Dakota, reached highest densities 1-5 years (Johnson 1997) and 6-7 years postfire (Madden 1996).
Common on an idle control (Johnson 1997), and, although they reached their highest density 6-7 years postfire, no significant response to fire (Madden 1996). Fire reduced abundance on native fescue (FESTUCA ALTAICA) for 3 years in Saskatchewan (Pylypec 1991). However, in Illinois, preferred recently burned grassland for nesting (Herkert 1994). Densities were highest in grasslands the first growing season postfire, lower on grasslands the second growing season postfire, and were not encountered > 3 growing seasons postfire (Herkert 1994).
MOWING/HAYING: In Alberta, nesting densities were highest in undisturbed (>3 growing seasons since last mowing) grasslands, but they also nested in grasslands that had been mowed the previous summer (Owens and Myres 1973). In Saskatchewan, more abundant in tame hayland idled for > 3 years than in annually hayed tame vegetation or in idle native prairie (Dale 1992, Dale et al. 1997). In Manitoba, most abundant and most productive in hayland compared to native grassland, tame grasslands, and woodlands; productivity was evaluated using a behavioral index that ranked behavior indicative of nestling or fledgling care (Jones 1994). Abundance was highest in recently (within 4 months of 1 May) mowed grasslands, which provided the low-to-medium vegetation height preferred by this species (Herkert 1991). In Michigan, abundance was reduced after hayfields were mowed, and mowing exposed nests and young to predators (George 1952). On seven rural Illinois airports, mowing destroyed 44 percent of all grassland bird nests, and Savannah Sparrow nest success was 23 percent (Kershner and Bollinger 1996).
GRAZING: In short- and mixed-grass prairie, moderately and heavily grazed areas do not provide the dense ground cover required by nesting birds (Dale 1983). Several studies conducted in the Great Plains reported higher nesting densities on idle or lightly grazed grasslands compared to moderately or heavily grazed areas (Owens and Myres 1973; Maher 1974,1979; Kantrud 1981; Kantrud and Kologiski 1982; Anstey et al. 1995). For example, average breeding densities were 7.7 pairs per hectare in ungrazed versus 0.3 pair per hectare in grazed grasslands (Maher 1979). In Tennessee, no longer used a grassy field after it was heavily grazed (Knight 1989). In Idaho, used both grazed and ungrazed riparian habitats, but were more abundant in ungrazed areas (Medin and Clary 1990).
Although heavily grazed areas are unsuitable for nesting, grazing can be used to improve habitat. In North Dakota, densities of were highest in fields one year postgrazing, followed by dense nesting cover (DNC), grazed, and idle fields (Renken 1983). In Saskatchewan, foraged most frequently in grazed grasslands, but the number of nesting pairs was consistently lower in grazed than ungrazed areas (Dale 1984). Herkert et al. (1993) recommended light grazing, resulting in > 40 percent vegetative cover > 25 cm tall, to produce the intermediate vegetation height and density. In Alberta, frequency of occurrence did not significantly differ between four grazing treatments: early season tame (grazed from late April to mid-June), early season native (grazed in early summer), deferred grazed native (grazed after 15 July), and continuously grazed native (Prescott and Wagner 1996). In North Dakota, densities did not differ significantly between season-long (continuously grazed), short-duration, and twice-over rotation grazing treatments (Messmer 1990). Short-duration grazing involves a system of pastures rotated through a grazing schedule of approximately one week grazed and one month ungrazed, repeated throughout the season. Twice-over rotation involves grazing a number of pastures twice per season, with about a 2 month rest in between grazing. Season-long grazing involves leaving a herd on the same pasture all season. Higher densities of Brown-headed Cowbirds were observed in summer-grazed versus winter-grazed pastures in Colorado, and Knopf et al. (1988) cautioned that summer grazing could lower reproductive success of Savannah Sparrows and other grassland-nesting birds.
CULTIVATION/CROPLAND: In Saskatchewan, were more abundant in hayland and tame pasture than in native pasture, and were detected least frequently in cropland (Anstey et al. 1995); in Alberta, the species also occurred more frequently in tame than native pasture (Prescott and Murphy 1996). In native pasture, preferred low to moderate cover diversity and moderate to tall grass; in tame pasture, the species preferred high herbaceous biomass (Prescott and Murphy 1996). However, another Saskatchewan study found that Savannah Sparrow occurred more frequently on native pasture than on pastures seeded to pure crested wheatgrass (AGROPYRON CRISTATUM); no difference was found in frequency of occurrence when native pastures were compared to pastures of crested wheatgrass/grass (brome [BROMUS INERMUS] and Kentucky bluegrass (POA PRATENESIS) or crested wheatgrass/alfalfa (MEDICAGO SATIVA) (Davis and Duncan, in press).
In eastcentral Saskatchewan, were as common in fallow cropland as in two kinds of planted cover (Dale 1993). In Manitoba, Savannah Sparrows were as equally abundant in native DNC as in tame DNC and native grassland (Dhol et al. 1994). However, they were more productive in native DNC than in native grassland. Avian productivity was evaluated using a behavioral index that ranked behavior indicative of nestling or fledgling care. Most abundant in 1-3 years old DNC fields in Alberta, although they were present in all age classes studied (0-5 years since seeding) (Prescott and Murphy 1995).
In Alberta, abundance and productivity increased when winter and spring wheat were minimum tilled rather than conventional tilled (Dale and McKeating 1996). In Iowa, Savannah Sparrows nested at low densities in nontilled fields of corn and soybeans that were idle in fall and spring and contained year-round crop residue, rather than in tilled fields (Basore et al. 1986). In North Dakota, very few were found nesting in any type of cropland (conventional tillage, minimum-tillage, and organic fields in fallow, sunflowers, or wheat) (Lokemoen and Beiser 1997). Minimum-tillage and organic fields had more vegetation and attracted greater numbers and species of birds, but predation and mechanical activities resulted in low reproductive success (Lokemoen and Beiser 1997). Conservation tillage (reduced and no-tillage) may create ecological traps, as grassland nesting birds are attracted to the habitat provided, but have low nesting success (Best 1986).