The Field Sparrow is a common songbird of eastern North America, breeding in brushy pastures and second-growth scrub, but avoiding similar habitat in developed areas, such as suburbs. Its breeding range covers much of the eastern United States and southern Canada. Winter range is slightly south of the breeding range and greatly overlaps it. Wintering habitat appears similar to breeding, but is not well studied. A partial migrant, some individuals remain on or near their breeding grounds in winter while others move farther south. This sparrow is well recognized for its distinctive song of pure tones, heard throughout the summer – an accelerating series of soft, sweet whistles that start with long duration tones and increase in rate to a trill. Both sexes are alike in plumage, rusty brown on the back and crown with white to light gray unstreaked breasts. Its pinkish bill and legs are considered distinctive. Typically males are slightly larger than females.

The nests of this species, composed almost exclusively of grasses, are located near the ground in early spring, typically at or near the base of woody vegetation. Later nests are built in small saplings and shrubs (usually < 1 m high) as ground cover increases in height. Pairs renest rapidly following predation or desertion. Only females incubate eggs, but both sexes share roughly equally in the feeding of young. On average ~40% of nests fledge young, and double brooding is common. While adults are faithful to breeding sites (~50% return in the following year), young rarely return to their natal area. Although by no means threatened, the Field Sparrow appears to be declining in numbers, most likely due to changes in their breeding habitat as shrubby old fields succeed to forest or are cleared for agriculture or suburban growth.

The species was the subject of a long-term breeding study: 1938 through 1948 in Calhoun County, Michigan ( Walkinshaw, L. H. (1978a). Life history of the eastern Field Sparrow in Calhoun County, Michigan. Ann Arbor, MI: University Microfilm International. Close Walkinshaw 1978a), with less focused studies covering the period from 1919–1968 ( Walkinshaw, L. H. (1936). Notes on the Field Sparrow in Michigan. Wilson Bulletin 48:94-101. Close Walkinshaw 1936, Walkinshaw, L. H. (1939c). Nesting of the Field Sparrow and survival of the young. Bird-Banding 10:107-114, 149-157. Close Walkinshaw 1939c, Walkinshaw, L. H. (1945). Field Sparrow, 39-54015. Bird-Banding 16:1-14. Close Walkinshaw 1945, Walkinshaw, L. H. (1978a). Life history of the eastern Field Sparrow in Calhoun County, Michigan. Ann Arbor, MI: University Microfilm International. Close Walkinshaw 1978a). A short term in-depth study of breeding biology was carried out in Platt County, Illinois from 1971–1972 by Best ( Best, L. B. (1974c). Breeding ecology of the Field Sparrow, Spizella pusilla. Phd Thesis, Univ. Illinois, Urbana. Close Best 1974c, Best, L. B. (1974a). An unusual case of nesting persistence in a female Field Sparrow. Condor 76:349. Close Best 1974a, Best, L. B. (1974b). Blue racers prey on Field Sparrow nests. Auk 91:168-169. Close Best 1974b, Best, L. B. (1977b). Nestling biology of the Field Sparrow. Auk 94:308-319. Close Best 1977b, Best, L. B. (1977d). Territory quality and mating success in the Field Sparrow (Spizella pusilla). Condor 79:192-204. Close Best 1977d, Best, L. B. (1977c). Patterns of feeding Field Sparrow young. Wilson Bulletin 89:625-627. Close Best 1977c, Best, L. B. (1978). Field Sparrow reproductive success and nesting ecology. Auk 95:9-22. Close Best 1978, Best, L. B. (1979). Effects of fire on a Field Sparrow population. Am. Mid. Nat. 101:434-442. Close Best 1979). More recently, Burhans, Thompson, and colleagues have closely studied the impacts of predators and the Brown-headed Cowbird (Molothrus ater) on the species, primarily focusing their work in central Missouri ( Burhans, D. E. (1997). Habitat and microhabitat features associated with cowbird parasitism in two forest edge cowbird hosts. Condor 99 (4):866-872. Close Burhans 1997, Burhans, D. E. (2000a). "Morning nest arrivals in cowbird hosts: their role in aggression, cowbird recognition, and host response to parasitism." In Ecology and management of cowbirds and their hosts., edited by J. N. M. Smith, T. L. Cook, S. I. Rothstein, S. K. Robinson and S. G. Sealy, 161-168. Austin: Univ. Texas Press. Close Burhans 2000a, Burhans, D. E. (2001b). Enemy recognition by Field Sparrows. Wilson Bulletin 113 (2):189-193. Close Burhans 2001b, Burhans, D. E. and F. R. Thompson III. (2006). Songbird abundance and parasitism differ between urban and rural shrublands. Ecological Applications 16 (1):394-405. Close Burhans and Thompson III 2006, Burhans, D. E., F. R. Thompson and J. Faaborg. (2000). Costs of parasitism incurred by two songbird species and their quality as cowbird hosts. Condor 102:364-373. Close Burhans et al. 2000, Burhans, D. E., B. M. Strausberger and M. D. Carey. (2001). Regional variation in response of Field Sparrows to the threat of Brown-headed Cowbird parasitism. Auk 118 (3):776-780. Close Burhans et al. 2001, Burhans, D. E., D. Dearborn, F. R. Thompson III and J. Faaborg. (2002). Factors affecting predation at songbird nests in old fields. Journal of Wildlife Management 66 (1):240-249. Close Burhans et al. 2002, Strausberger, B. M. and D. E. Burhans. (2001). Nest desertion by Field Sparrows and its possible influence on the evolution of cowbird behavior. Auk 118 (3):770-776. Close Strausberger and Burhans 2001, Thompson III, F. R. and D. E. Burhans. (2003). Predation of songbird nests differs by predator and between field and forest habitats. Journal of Wildlife Management 67 (2):408-416. Close Thompson III and Burhans 2003). Structure and function of the song was the subject of a series of studies carried out by Nelson and colleagues ( Nelson, D. A. (1988a). Feature weighting in species song recognition by Field Sparrows (Spizella pusilla). Behaviour 106:158-182. Close Nelson 1988a, Nelson, D. A. (1989b). Song frequency as a cue for recognition of species and individuals in the Field Sparrow (Spizella pusilla). J. Comp. Psychol. 103:171-176. Close Nelson 1989b, Nelson, D. A. (1989c). The importance of invariant and distinctive features in species recognition of bird song. Condor 91:120-130. Close Nelson 1989c, Nelson, D. A. (1992b). Song overproduction and selective attrition lead to song sharing in the Field Sparrow (Spizella pusilla). Behav. Ecol. Sociobiol. 30:415-424. Close Nelson 1992b, Nelson, D. A. and L. J. Croner. (1991). Song categories and their functions in the Field Sparrow. Auk 108:42-52. Close Nelson and Croner 1991). MC has carried out a long-term breeding study covering the years 1987 through 2006 (and still ongoing) in Lackawanna County, Pennsylvania (see Carey [ Carey, M. (1990). Effects of brood size and nestling age on parental care by male Field Sparrows (Spizella pusilla). Auk 107:580-586. Close Carey 1990]). This study remains largely unpublished, but all references to MC in this account refer to data from that study.