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Spizella pusillafield sparrow

By Tanya Dewey

Geographic Range

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)

Habitat

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)

Physical Description

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)

  • Sexual Dimorphism
  • male larger
  • Range mass
    11.4 to 15.7 g
    0.40 to 0.55 oz
  • Range length
    12.5 to 15 cm
    4.92 to 5.91 in

Reproduction

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)

  • Breeding interval
    Field sparrows breed in the warm season, attempting several clutches in each breeding season. From 2.9 to 4 clutch attempts per breeding is typical.
  • Breeding season
    Breeding occurs throughout much of the warm season, with eggs laid from April through August.
  • Range eggs per season
    2 to 5
  • Range time to hatching
    10 to 17 days
  • Average time to hatching
    11-12 days
  • Range fledging age
    7 to 8 days
  • Range time to independence
    24 to 36 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

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)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifespan/Longevity

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)

  • Average lifespan
    Status: wild
    8.75 years

Behavior

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)

Home Range

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)

Communication and Perception

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)

Food Habits

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)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • seeds, grains, and nuts

Predation

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)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

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)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

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)

Economic Importance for Humans: Negative

There are no adverse effects of field sparrows on humans.

Conservation Status

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)

Contributors

Tanya Dewey (author), Animal Diversity Web.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

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.

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