Spizella pusilla
field sparrow

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 substantially and they are found year-round throughout much of their range except for the northernmost and southernmost portions. Some populations are resident year-round while others undertake short migrations. (Carey, et al., 2008)

Field sparrows can be common in preferred habitat, but are rarely found near human habitation, even in appropriate habitat. They are found in open, savanna-like habitats, such as successional 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. Once succesional habitats become overgrown with trees and shrubs, field sparrows are no longer found there. (Carey, et al., 2008)

Male field sparrows are slightly larger than females, but both sexes have similar plumage. 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. They might be confused with Worthen's sparrows (Spizella wortheni) in southern New Mexico, but they lack the rufous stripe from the eye, a different song, and black legs. (Carey, et al., 2008)

Field sparrows are monogamous. Males seem to use their simple songs to attract a mate, the frequency of simple songs decreases after a pair bond forms. Males accompany females during nest building and begin copulatory behavior while the nest is being built. Females seem to find a male mate within a few days of arriving in their breeding area and remain with their mate for a breeding season. A small number of individuals mate with each other again in following years. Extra-pair copulations have been observed. (Carey, et al., 2008)

Field sparrows breed from April through August each year. They lay up to 4 clutches per breeding season. Multiple nesting attempts are typical because of high rates of nest predation and desertion. Fledglings still dependent on their parents have been observed as late as October. Females choose a nest site and construct a bowl-like nest of woven grass in vegetation near trees and saplings. Nests early in the season are built on or near the ground, but later in the season, after woody vegetation has leafed out, they may be in the branches of shrubs or small trees. 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 elsewhere. Females lay from 2 to 5 eggs and begin incubating just before the last egg is laid. Females may delay incubation until well after the last egg is laid if the weather is cold and wet. Incubation is generally from 11 to 12 days long, but can be from 10 to 17 days. Young fledge 7 to 8 days after hatching, begin to fly at 13 to 14 days after hatching, and become independent within 24 to 36 days after hatching. Young are sexually mature in the year following their hatching. (Carey, et al., 2008; NatureServe Explorer, 2008)

Females incubate eggs and brood hatchlings, spending about 70% of their time on the nest. Males will occasionally feed incubating females. Males and females feed hatchlings approximately equally. Young are altricial at hatching and mostly naked. They develop gray downy plumage, their eyes open at 4 days old, and they can stand by about 5 days old. Parents continue to feed their young through the hatchling phase and into the post-fledging period; they feed and protect young for 26 to 34 days after hatching, about 17 to 28 days after fledging. Males can take over feeding of fledglings if the female begins to construct another nest to begin a subsequent brood. (Carey, et al., 2008)

Maximum recorded age in the wild is 8 years 9 months, based on banding records. Annual male survivorship is estimated at 53% and annual female survivorship at 36%. Winter range conditions may result in higher mortality. Approximately 50% of fledglings are thought to die before the fall of their hatch year. (Carey, et al., 2008)

Field sparrows are found in territorial, mated pairs during the breeding season and in small flocks during the winter and migration. Breeding territories are established with song and perhaps some male-male aggression, but field sparrows are generally reported to be non-aggressive. They forage mainly on the ground, hopping along to discover seeds, and sleep on perches in woody vegetation. Some populations undertake small migrations but other populations remain resident year-round. (Carey, et al., 2008)

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, consisting 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. (Carey, et al., 2008)

Field sparrows take seeds, primarily 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, breeding season they also take adult and larval insects and spiders. They forage on the ground, most often near some form of vegetative cover. In the breeding season field sparrows forage on their own or with a mate, but they form small foraging flocks in winter. They take fallen seeds or land on grass stems and push them to the ground, where they remove the seeds. They use perches to briefly scan for insect prey. (Carey, et al., 2008; NatureServe Explorer, 2008)

Observed predators of eggs and nestlings include chipmunks (Tamias striatus) and many species of snakes (Pantherophis obsoletus, Coluber constrictor, Lampropeltis, Thamnophis sirtalis, Lampropeltis calligaster). The most common predators recorded are black rat snakes (Pantherophis obsoletus). Likely predators include red foxes (Vulpes vulpes), grey foxes (Urocyon cineoargenteus), weasels (Mustela), mink (Neovison vison), skunks (Mephitis mephitis), raccoons (Procyon lotor), and opossums (Didelphis virginianus). 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. (Carey, et al., 2008)

Many kinds of ectoparasites are found on field sparrows, including feather mites. They are also infected by Plasmodium species. Field sparrows are important predators of grass seeds in their savanna and edge habitats. Nests are parasitized by brown-headed cowbirds (Molothrus ater), although frequency varies regionally. Most parasitized nests are deserted by the female. If a field sparrow nest is successfully parasitized by brown-headed cowbirds, their overall nesting success is greatly reduced and few of the cowbird nestlings are successfully raised. (Carey, et al., 2008)

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)

There are no adverse effects of field sparrows on humans.

Field sparrows are sensitive to habitat disturbance and have fairly narrow habitat preferences. They are not found in areas with human habitations, which are expanding currently. Available habitat may increase in areas with recent forest cutting, or decrease in areas with predominantly successional habitats, which become inappropriate for field sparrows as they grow. 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. (Carey, et al., 2008; NatureServe Explorer, 2008)