Habitat
Habitat includes grasslands, savannas, cultivated fields, and pastures, in lowland and mountain valleys, foothills, and open mountains (Subtropical and Temperate zones) (AOU 1998), nesting at elevations as high as 3,110 meters in Colorado (Kingery 1998). Female builds nest on dry ground. Nest is a large domed structure of woven grasses and ground vegetation.
Grassland habitat range from shrubsteppe and shortgrass prairie to mixed-grass and tallgrass prairie (Bent 1958, Maher 1974, Stewart 1975, Salt and Salt 1976, Dale 1983, Laubach 1984, Bock and Bock 1987, Renken and Dinsmore 1987, Lanyon 1994, Bock et al. 1995). In the Great Plains, this species uses a wide range of vegetation heights and densities, although it avoids extremely sparse or tall cover (Dale 1983, Patterson 1994, Patterson and Best 1996), preferring high forb and grass cover, low to moderate litter cover, and little or no woody cover (Sample 1989, Kimmel et al. 1992, Anstey et al. 1995, Hull et al. 1996, Madden 1996). In shrubsteppe and desert grasslands, it prefers mesic areas; low shrub cover and density; patchiness in vegetative structure and in heights of forbs and shrubs; and high coverage of grass, forb, and litter (Lanyon 1962, Rotenberry and Wiens 1980, Wiens and Rotenberry 1981, Wiens et al. 1987, McAdoo et al. 1989, Knick and Rotenberry 1995). In general, open, treeless areas are most suitable (Salt and Salt 1976, Sample 1989, Johnson 1997), although a few shrubs may be used as song perches (Knick and Rotenberry 1995).
Suitable habitats are found in idle native and idle tame grasslands (including fields of planted cover, such as Conservation Reserve Program [CRP] fields, Permanent Cover Program [PCP] fields, and dense nesting cover [DNC]), native and tame pastures and hayland (Graber and Graber 1963; Giezentanner 1970; Maher 1973, 1974; Stewart 1975; Salt and Salt 1976; Johnsgard 1979, 1980; Ducey and Miller 1980; Kantrud 1981; Kantrud and Kologiski 1982; Faanes 1983; Laubach 1984; Renken and Dinsmore 1987; Frawley and Best 1991; Dhol et al. 1994; Hartley 1994; Klute 1994; Anstey et al. 1995; Berthelsen and Smith 1995; Bock et al. 1995; Faanes and Lingle 1995; King and Savidge 1995; Prescott et al. 1995; Skeel et al. 1995; Sutter 1996; Delisle and Savidge 1997; Klute et al. 1997; Prescott 1997; Davis and Duncan 1999). Road rights-of-way, field edges, cropland, retired cropland, wet meadows, pine (PINUS) foothills, mountain meadows, orchards, windbreaks, riparian areas, and to a limited extent, wet areas on shortgrass prairie and sagebrush (Artemisia)-dominated plains also are used (Hergenrader 1962, Bent 1958, Strong 1971, Stewart 1975, Salt and Salt 1976, Johnsgard 1979, Ducey and Miller 1980, Stauffer and Best 1980, Faanes 1983, Basore et al. 1986, Cable et al. 1992, Camp and Best 1993, Hartley 1994, Lanyon 1994, Faanes and Lingle 1995, Prescott 1997).
Within mixed-grass areas in North Dakota, abundance was positively associated with percent grass cover, litter depth, and density of low-growing shrubs (western snowberry [Symphoricarpos occidentalis] and silverberry [Eleagnus commutata]; Schneider 1998). In mixed-grass prairie in North Dakota, density was positively correlated with maximum and average vegetation heights, and negatively correlated with shrub coverage (George and McEwen 1991). When vegetation variables were grouped and analyzed in combination, western meadowlark density was positively correlated with vertical density of vegetation and grass cover, and negatively correlated with vertical heterogeneity (diversity of vegetation) and litter cover.
In riparian areas in Iowa, density was positively associated with grass cover and the cover of all life forms combined (life forms were defined as grass-like vegetation, forbs, shrubs, deciduous and evergreen trees, and vines; Best et al. 1981). Density was negatively associated with sapling and tree richness, the horizontal patchiness of trees, and forb cover.
In crested wheatgrass (Agropyron cristatum) pastures in Saskatchewan, abundance was positively correlated with litter depth and the number of plant contacts from 0 to 10 centimeters from the ground (Sutter and Brigham 1998). Numbers were higher in areas with high percent grass and sedge cover and high maximum vegetation height than in areas with high litter depth and number of plant contacts more than 10 centimeters tall. In mixed-grass pastures, density was negatively correlated with maximum vegetation height and the number of plant contacts less than 10 centimeters. Numbers were higher in areas with high percent grass and sedge cover and high maximum vegetation height than in areas with high litter depth and number of plant contacts more than 10 centimeters tall. In Nebraska, western meadowlarks were equally abundant in idle fields planted to native grasses and in idle fields planted to tame grasses (Delisle and Savidge 1997). In Saskatchewan, they occurred with equal frequency in native pastures and tame pastures (Anstey et al. 1995, Sutter 1996, Davis and Duncan 1999). In Manitoba and Alberta, however, they preferred native grasses to tame grasses (Wilson and Belcher 1989, Dhol et al. 1994, Prescott and Murphy 1996).
Nests were found in grassed waterways planted to smooth brome (Bromus inermis) in Iowa rowcrop fields (Bryan and Best 1991). Occasionally nest occur in no-till cropland (Basore et al. 1986). In Iowa, western meadowlarks preferred untilled fields of corn and soybeans rather than tilled fields (Basore et al. 1986). Untilled fields were idle in the fall and spring and contained year-round crop residue. Specifically, they preferred nesting in fields where corn was planted into sod residue over fields where corn or soybeans were planted into corn residue (Basore et al. 1986). In wheat-stubble fields, the tightly woven nest often protected eggs from rolling out during tillage with undercutter blades (Rodgers 1983).
In South Dakota mixed-grass prairies, densities were higher in large grassland patches (> 50 hectares) than smaller ones (Bakker et al. 2002).
Ecology
This species occurs in flocks of up to 10-75 birds in winter.
Predators include: hawks, crows, skunks, weasels, raccoons, and coyotes.
This species is regarded as an intolerant host of the brown-headed cowbird (Molothrus ater) in some areas and is known to eject the eggs of this parasitic species (Hergenrader 1962). Brood parasitism rates of more than 40 percent, however, have been recorded (Davis 1994; Klute 1994; Koford et al., in press), although other studies have recorded lower parasitism rates (Hergenrader 1962, Friedmann 1963, Bent 1958, Maher 1973, Hill 1976). In Manitoba, a relatively high brood parasitism rate of 44 percent on 65 nests was recorded (Davis 1994; Davis and Sealy 2000). Within native grasslands in North Dakota, frequency of brood parasitism on 294 nests was 47 percent; within Conservation Reserve Program (CRP) and dense nesting cover (DNC) grasslands, the frequency of brood parasitism on 26 nests was 19 percent (Koford et al., in press). Within annually burned and moderately grazed tallgrass pastures in Kansas, the brood parasitism rate for 6 nests was 83 percent (Klute 1994).