Northern Prairie Wildlife Research Center
Lark sparrows prefer to nest in disturbed, open habitats characterized by short vegetation and large amounts of bare ground where there are boulders, fenceposts, or small trees that can be used by singing males. In the Oak Openings of northwestern Ohio, lark sparrows nested in sparsely vegetated fields and on sandy beach ridges. In southeastern Ohio, nesting pairs preferred rocky, overgrazed, hillside pastures. Lark sparrow nests also have been found in abandoned quarries, gravel pits, and along the margins of cultivated fields with sandy soils (Peterjohn 1989, Peterjohn and Rice 1991).
Lark sparrows occupy markedly different habitats in Ohio than elsewhere in their range (Peterjohn 1989). Bent (1968) stated that lark sparrows in the central and eastern United States nested in areas with scattered trees, weedy forbs, and much bare ground. Herkert et al. (1993) did not consider lark sparrows true prairie birds (i.e., grassland specialists) and believed that the species only recently invaded grassland habitats in the Midwest. Lark sparrows have been reported nesting in grasslands with scattered trees and shrubs (Wiens 1963, Walcheck 1970, Crowell et al. 1982, McNair 1982), pastures (Newman 1970; Crowell et al. 1982; McNair 1982, 1983), tallgrass prairie (Hill 1976, Crowell et al. 1982, Herkert et al. 1993), CRP grasslands (Lauber 1991, Johnson and Schwartz 1993b), sagebrush grassland (Walcheck 1970, Rumble 1987), semi-desert grassland (Bock and Webb 1984), and a cultivated peanut field (Newman 1970).
Most lark sparrow nests were placed on the ground under clumps of grass and herbaceous cover, although some nests were found </=1 m above ground in dense brambles (Newman 1970, McNair 1985, Peterjohn and Rice 1991). Vegetative characteristics of habitats occupied by nesting lark sparrows in Arizona were 4% woody cover, 52% grass cover, 7% forb cover, 37% bare ground, and 13-cm mean grass canopy height (Bock and Webb 1984). Caterpillars (Lepidoptera) were considered the most important nestling food and grasshoppers the most important fledgling food (McNair 1982).
Bock and Webb (1984) found higher nesting densities of lark sparrows on grazed than ungrazed semidesert grassland in Arizona. Newman (1970) and McNair (1983) also noted that lark sparrows nested in heavily-grazed pastures where cattle kept the vegetation cropped close to the ground.
Samson (1980) estimated that 10-100 ha represented the minimum amount of contiguous grassland habitat required to maintain a viable breeding population of lark sparrows. Habitat loss due to spreading agriculture was considered the major factor contributing to lark sparrows becoming rare or absent in parts of South Dakota over a 68-year period (Blankespoor and Krause 1982).