Male field sparrows are slightly larger than females, but both sexes have similar feather color. They are reddish brown on their heads and back with gray, un-streaked bellies. They have two white wing bands, a white eye ring, and a rusty brown stripe extending from the eye. Their bill and legs are pinkish, helping to distinguish them from other sparrows.
Field sparrows are found throughout the eastern United States from just east of the Rocky Mountains to the Atlantic Coast and from North Dakota to southern Texas in the west and New Hampshire to Florida in the east. They are also found in southern Ontario and southernmost Quebec. Their breeding and wintering ranges overlap and they are found year-round throughout much of their range.
Field sparrows can be common in habitats they like but they don't like living near humans. They are found in open, savanna-like habitats, like old fields, forest edges and openings, fencerows and road or railway cuts near open fields, and occasional orchards and nurseries. They are found only in fields with some trees or shrubs that provide perches, but not too many trees.
Field sparrows form mated pairs that stay together during the breeding season. Males use their simple songs to attract a mate and then stay near her as she builds a nest and begins to lay eggs.
Field sparrows breed from April through August each year. They lay from 2 to 5 eggs in up to 4 clutches per breeding season. Field sparrows often have to try nesting several times before being successful, because they have lots of predators. Females choose a nest site and construct a bowl-like nest of woven grass. During egg laying the parents don't seem to protect the nest. If eggs are taken by predators, the parents will attempt to build a new nest somewhere else. Incubation is generally from 11 to 12 days long. Young begin to fly at 13 to 14 days after hatching and become independent within 24 to 36 days after hatching. Young can breed in the year following their hatching.
Females incubate eggs and keep the hatchlings warm, spending about 70% of their time on the nest. Males will occasionally feed the females. Males and females feed hatchlings about equally. Young are naked and helpless when they hatch. They develop gray downy feathers, their eyes open at 4 days old, and they can stand by about 5 days old. Parents continue to feed their young for 26 to 34 days after hatching, about 17 to 28 days after they can fly.
Field sparrows have lived up to 8 years 9 months in the wild. Approximately 50% of young are thought to die before the fall of the year they were hatched.
Field sparrows are found in mated pairs during the breeding season and in small flocks during the winter and migration. Mated pairs defend small breeding territories. They forage mainly on the ground, hopping along to discover seeds, and sleep on perches in woody vegetation. Some populations make small migrations but other populations remain resident year-round.
Breeding territory sizes were estimated at an average 0.76 ha (range 0.31 to 1.62 ha) in one population. (Carey, et al., 2008)
Field sparrows are recognized by their distinctive, pretty song, made up of soft whistles that accelerate towards a trill. Males use songs to advertise territories during the breeding season. Young field sparrows learn songs from their parents. Field sparrows also have a repertoire of other calls, including a foraging note ("seep"), courtship calls, trill calls used in territorial defense and courtship, cricket calls used by females at the nest, chip calls given in the presence of a threat, and "zeeee" or "eeeee" calls used with threats.
Field sparrows eat mainly grass seeds, throughout the year. Grass seeds make up less than 50% of their diet in the summer, but more than 90% in the winter. In the summer they also take adult and larval insects and spiders. They forage on the ground, most often near some form of plant cover.
Predators of eggs and nestlings include chipmunks and many species of snakes (rat snakes, blue racers, milk snakes, garter snakes, and prairie kingsnakes). The most common predators recorded are black rat snakes. Likely predators include red foxes, grey foxes, weasels, mink, skunks, raccoons, and opossums. Field sparrows use a "chip" call to alert others to a threat. They will use a broken-wing display to distract predators from their nest.
Many kinds of parasites are found on field sparrows, including feather mites. Field sparrows are important predators of grass seeds in their savanna and edge habitats. Nests are parasitized by brown-headed cowbirds. Most parasitized nests are deserted by the female.
There are no adverse effects of field sparrows on humans.
There are no direct positive impacts of field sparrows on humans. They are an interesting member of the native, North American bird fauna and are appreciated for their song. (Carey, et al., 2008)
Field sparrows are sensitive to habitat disturbance and are found in only specific kinds of open, savanna habitats. They are not found in areas disturbed by humans, which are expanding currently. Populations have experienced declines across their range, but field sparrows are widespread and fairly common where habitat is appropriate, so they are not considered threatened currently. However, populations in Colorado are considered critically imperiled and populations in New Hampshire, Massachusets, Maine, Quebec, and the Canadian maritime provinces are considered vulnerable.
Tanya Dewey (author), Animal Diversity Web.
Carey, M., D. Burhans, D. Nelson. 2008. Spizella pusilla. Birds of North America, 103: 1-20. Accessed March 27, 2009 at http://bna.birds.cornell.edu/bna/species/103.
NatureServe Explorer, 2008. "Spizella pusilla" (On-line). NatureServe Explorer. Accessed March 27, 2009 at http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Spizella%20pusilla.