Breeding Habitat:Grassland
Nest Type:Open-cup nesting passerine
Migration Status:Short distance migrant
Nest Location:Ground-low nesting
Breeding Vesper Sparrows are characteristic of relatively dry and sparsely vegetated areas with scattered tall structures used for song perches. These features may be found in a variety of habitats. In eastern North America, breeding pairs are most frequently found in pastures, hayfields, and along the edges of cultivated fields where hedgerows, scattered trees, power lines, or other tall structures can be used as song perches. However, they have been found in other habitats, including fallow fields in early stages of succession, gravel pits, golf courses, young pine plantations, open disturbed woodlots, and reclaimed strip mines (Brauning 1992, Laughlin and Kibbe 1985, Peterjohn and Rice 1991). This species occupies similar habitats on the Great Plains, while in western North America, they are also regularly found in sagebrush and other open shrublands mixed with grasses as well as open pinyon-juniper woodlands (Andrews and Righter 1992).
Given these broad habitat preferences, Vesper Sparrows are fairly widespread summer residents in the United States and Canada. Along BBS routes, this species is most numerous from Minnesota and Iowa across North Dakota and the prairie provinces to Montana, Idaho, Wyoming, and southwestern Oregon. It is also locally numerous east to portions of Michigan and western Ohio (Relative Abundance Map).
As is true for many grassland birds, the breeding distribution of Vesper Sparrows has noticeably changed during historic times. During the nineteenth century, it underwent a marked range expansion into the northeastern U.S. and adjacent Canada, becoming relatively numerous in many areas (Andrle and Carroll 1988, Brewer et al. 1991, Laughlin and Kibbe 1985). This range expansion was in response to deforestation and the prevalence of agriculture in this portion of their range. Since the 1940s, however, many of the farmlands have disappeared, producing a noticeable reduction in Vesper Sparrow populations throughout the northeast.
Over the entire BBS survey period, significant declines occur in 11 states, 12 physiographic strata, the Eastern BBS Region, U.S., and survey-wide. Increases are limited to 3 states and 3 strata, while the other regional trends estimates are close to zero (Trend List). The 1966-1979 trends are similar. Only 3 states and 2 strata show significant increases during this interval, while declines are recorded in 9 states, 12 strata, the Eastern BBS Region, US, Canada, and survey-wide. The trend estimates are more positive after 1980, however, with increases in 6 states, 5 strata, the Central and Western BBS regions, and Canada. Significant declines are evident in 7 states, 8 strata, and the Eastern BBS Region during the latter interval. The trend map shows fairly consistent declines from Minnesota, Wisconsin, and Indiana eastward (Trend Map). Declines also prevail from Montana and South Dakota south to northern New Mexico and northern Arizona, and also from western Washington south into Nevada. Increasing populations predominate from Illinois across Iowa to Kansas, and from North Dakota into the prairie provinces.
The survey-wide indices are variable, but declines are most evident prior to the mid-1970s (Survey-wide Annual Indices). This variability is largely a result of similar trends in the Central and Western BBS regions; populations in the Eastern BBS Region have declined throughout the survey period (Eastern BBS Region Annual Indices). A variety of temporal patterns are exhibited for populations that are increasing or decreasing. For example, Vesper Sparrows in North Dakota show the most marked increases after the mid-1980s, while the Washington population has increased throughout the survey period (North Dakota Annual Indices) (Washington Annual Indices). The Iowa population has a variable pattern with sharp increases followed by equally sharp declines, although with a general increasing tendency over the years (Iowa Annual Indices). In Oregon, Vesper Sparrows also fluctuate dramatically with noticeable increases followed by sharp declines, but the overall trend has remained relatively stable (Oregon Annual Indices). In Eastern North America, populations declined sharply through the late 1970s to very low numbers, followed by fairly stable trends (Maryland Annual Indices) (New York Annual Indices) (Ohio Annual Indices). The Indiana and Michigan populations decreased through the mid- 1970s, followed by a slight recovery and another decline after the early 1980s (Indiana Annual Indices) (Michigan Annual Indices). In contrast, Vesper Sparrows in Wisconsin have declined throughout the survey period (Wisconsin Annual Indices). There is no evidence suggesting this species was noticeably affected by the severe winter weather of 1976-1978.
Several factors contributed to the population declines in eastern North America. Loss of grassland habitat to reforestation and urbanization are major factors, although "clean farming" practices such as the removal of hedgerows and the more frequent mowing of hayfields also have contributed to these declines (Brauning 1992, Laughlin and Kibbe 1985). However, Vesper Sparrows are one of the first species to occupy strip mines once they have been reclaimed (Whitmore and Hall 1978), causing them to expand their range in heavily forested portions of West Virginia and surrounding states in recent years.
Most wintering Vesper Sparrows occur across the southern tier of states, although small numbers are recorded on CBCs further north. These sparrows generally prefer weedy fields, the brushy borders of grasslands and hayfields, and desert scrub during this season. Wintering populations have significantly declined eastward from Texas and Arkansas, while non-significant increases tend to prevail in the southwestern states.
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