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Ammodramus savannarumgrasshopper sparrow

By Tanya Dewey

Geographic Range

Most grasshopper sparrow populations are migratory, wintering in the southern United States along the coastal plains of Virginia south through Florida, and along the Gulf of Mexico. They also winter throughout most of Mexico and into western Central America. They breed throughout most of the United States east of the Rockies, portions of southern Canada, and isolated populations in the western United States. Breeding is from southern Maine and Quebec to the Carolinas, through central Georgia, Alabama, and Mississippi, northernmost Louisiana, and most of Texas north to throughout most of Montana. They breed as far north in the plains region as southernmost Alberta, Saskatchewan, and Manitoba and throughout the Great Lakes region to southern Ontario. Isolated western populations include an area from southern British Columbia through eastern Washington and Oregon, an area of southern Idaho into northernmost Utah and Nevada, and portions of California, including coastal areas and the Sacramento Valley and western slopes of the Sierra Nevada. There are several populations that are resident year round, including portions of Central America and central Mexico, large parts of Texas, southernmost Arizona, and the central Gulf states, including Florida. They are also found year-round and wintering in the Greater Antilles Islands. (Vickery, 1996)

Habitat

Grasshopper sparrows prefer open grasslands with bare ground for foraging. In western, arid grasslands and prairies, grasshopper sparrows tend to be found in areas with shrub cover and more vegetation. In eastern, tallgrass prairies and moist grasslands, they tend to be found in areas of sparse vegetation. They are found in grasslands characterized by a wide variety of plants, including pine savannas, palmetto-sawgrass prairies, lowbush blueberry copses, and bunchgrass prairies. In the Appalachian Mountains these sparrows were once found up to 1550 m elevation on limestone outcroppings and "balds." Grasshopper sparrows seem to prefer areas with broad expanses of suitable habitat, not fragmented areas. Savannah sparrows (Passerculus sandwichensis) are most similar in habitat preferences to grasshopper sparrows. Other species with similar, but not completely overlapping, habitat preferences are Henslow’s sparrows, meadowlarks, bobolinks, and vesper sparrows. (Vickery, 1996)

Physical Description

Grasshopper sparrows are small sparrows, from 10.8 to 11.5 cm and from 14.5 to 20 g. They have robust bills, flesh colored legs, and streaked black and chestnut brown feathers on their back. Their breast and belly are unstreaked and creamy buff or white. They have a dark crown with a light colored crown stripe and yellowish plumage on the face surrounding the eyes which is disrupted by a dark line extending backwards from the eye. They have a relatively short tail and are considered stockier and bigger-headed than other, sympatric Ammodramus species. The intensity of plumage coloration varies geographically. Males and females are alike and juveniles have streaked breasts. (Vickery, 1996)

Grasshopper sparrows may be confused with Henslow's sparrows (Ammodramus henslowii), LeConte's sparrows (Ammodramus leconteii), Nelson's sharp-tailed sparrows (Ammodramus nelsoni), Baird's sparrows (Ammodramus bairdii), and savannah sparrows (Passerculus sandwichensis), although Baird's and savannah sparrows have streaked breasts. The best way to distinguish among Ammodramus sparrows is with their songs, as they are often difficult to observe. (Vickery, 1996)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    14.5 to 20 g
    0.51 to 0.70 oz
  • Range length
    10.8 to 11.5 cm
    4.25 to 4.53 in

Reproduction

Grasshopper sparrows are seasonally monogamous, although some polygyny has been described. Pairs are formed on the breeding grounds. Extra pair copulations are not reported, but more study is needed. Males use songs and a fluttering flight display to attract females. Males and females use contact calls throughout the breeding season to maintain the pair bond. Non-parental helpers at the nest are common, in one study 17% of nests had non-parental helpers, who made between 9 and 50% of visits to the nest with food. (Vickery, 1996)

Breeding season length and timing vary among grasshopper sparrow populations. Northern populations breed for about 90 days from May into August. In Florida and Jamaica, grasshopper sparrows breed twice yearly. Other populations breed either once or twice yearly and the timing of breeding varies. Pairs can attempt up to 3 broods in a year, although 2 is more typical. Males arrive on the breeding grounds a few days before females and establish territories. Pairs build nests immediately after forming in northern populations, up to 4 weeks after males begin singing in other populations. Females build cup-like nests on the ground, with a roof of grasses and a side opening. Nests are usually built of grasses, with finer materials lining the interior. New nests are built for each brood. Females lay from 3 to 6 (usually 4 to 5) eggs and incubate them for 11 to 13 days. Young leave the nest at 6 to 9 days old, but they leave the nest by running from it, rather than flying. Young leave the area of the nest immediately after fledging and are cared for to a limited extent by parents for an unknown time after that. Young can breed in the year following their hatching. (Vickery, 1996)

  • Breeding interval
    Grasshopper sparrows breed either once or twice yearly, varying with region.
  • Breeding season
    Breeding season varies regionally, from May into August in northern populations, from April to June and October to November in Jamaica, from March through June and then July to September in Florida, and from April to June in Panama and Haiti.
  • Range eggs per season
    3 to 6
  • Average eggs per season
    4-5
  • Range time to hatching
    11 to 13 days
  • Range fledging age
    6 to 9 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Females incubate the eggs and brood nestlings. Helpers at the nest may also brood nestlings. Young are altricial at hatching, developing their juvenile plumage at 10 to 12 days. Both parents and non-parental helpers at the nest will feed young. Males help to protect young by defending territories and keeping alert for predators. Young leave the nest at 6 to 9 days old and are cared for by parents for an unknown period after that. Based on inter-clutch intervals, this post-fledging care is from 4 to 19 days long. Young gather in small flocks at 3 to 4 weeks after hatching. Some may remain with parents as helpers at the nest. (Vickery, 1996)

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

Lifespan/Longevity

Grasshopper sparrows have an estimated average lifespan of 2.9 years. One individual lived 6.5 years in the wild. Annual survival of adults was estimated at 60%. (Vickery, 1996)

  • Range lifespan
    Status: wild
    6.5 (high) years
  • Average lifespan
    Status: wild
    2.9 years

Behavior

Grasshopper sparrows are diurnal, spending much of their time foraging, except during breeding season when males spend large amounts of time singing and displaying to defend breeding territories. Males mainly use songs and aggressive displays to defend their breeding territory. They are tolerant of their female mate and any helpers at the nest. Outside of the breeding season, grasshopper sparrows are not territorial and are not found in flocks. They use cryptic foraging behaviors and short, direct flights and are solitary when not breeding. (Vickery, 1996)

Northern populations of grasshopper sparrows are completely migratory, but southern populations are only partially migratory or are resident or make only small, regional movements seasonally. Fidelity to breeding sites seems to vary regionally, from 0 to 70% in different areas. (Vickery, 1996)

Grasshopper sparrows run or walk on the ground while foraging, although they may also hop occasionally. Their flight characteristics vary seasonally. Outside of the breeding season, flight is usually short and direct, with birds usually flying into some kind of cover. In the breeding season, flights are short and fluttery, with some zig-zagging behavior before flying into cover. Males use a fluttering flight when going between song perches or singing. (Vickery, 1996)

Home Range

Nesting territories are defended during the breeding season. Territory boundaries are determined by the placement of song perches. Territory sizes are reported to be from 0.19 to 1.8 hectares.

Communication and Perception

Grasshopper sparrows get their common name for the buzzing, insect-like quality of their songs. They are one of the few sparrow species that sings 2 different songs; males sing one song for attracting a mate and another to defend a breeding territory. Their primary song is several staccato notes followed by a sustained, insect-like "zeeeeee" and seems to be mainly territorial. The secondary song is a squeaky set of notes varying in pitch and seems to be used primarily in mate attraction and maintaining the pair bond. Males and females also use a descending trill to communicate with their mate, announcing their presence at the nest. Males also sing a flight song. Songs are sometimes sung together, as in the primary song followed by the secondary song. Songs are generally restricted to the breeding season, with grasshopper sparrows being relatively quiet at other times of the year. They also have a set of calls that are used, most are staccato "chip" or "tsip" notes used to indicate alarm, beg for food, or maintain contact. (Vickery, 1996)

Grasshopper sparrows also use a variety of visual displays in communication. Males use a wing-flutter display when singing on a perch. They use this wing-flutter display in antagonistic interactions with other males as well. They will chase other males and maintain a posture with the head below the back to indicate aggression. Females rapidly quiver their wings towards the male as a signal of appeasement or readiness to copulate. (Vickery, 1996)

Food Habits

Grasshopper sparrows eat insects and seeds, with proportions varying seasonally. In the summer, they eat primarily insects, with about 69% of their diet being invertebrates and 39% seeds. In fall they eat mainly seeds, making up 71% of the diet, with 29% made up of invertebrates. Common seeds eaten are sedges (Cyperaceae) and panic grass (Panicum). Preferred insect prey are grasshoppers, mainly species in the genera Xiphidium, Scudderia, Hippiscus, and Melanopus, but especially the grasshopper species Cordillacris occipitalis. They will also eat other insects and spiders, as they are encountered. Grasshopper sparrows forage on the ground using vision to detect prey, so they require open areas and bare ground for good visibility. They capture grasshoppers by pinching them around the thorax, immobilizing them. They will remove hard, less digestible parts, such as legs, before feeding them to offspring. (Vickery, 1996)

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

Predation

Most predation is probably on eggs, nestlings, and fledglings. Grasshopper sparrow adults will perform broken-wing distraction displays near nests or fledglings to draw predators away. They also use alarm calls to signal the presence of a threat. They hide the location of nests by never flying directly to them. Instead they land a short distance away and run through the grass to the nest entrance. Similarly, when leaving, they run from the nest and then take flight at a distance from the nest. Grasshopper sparrows nests are widely dispersed and well-hidden, so predators mostly happen upon them by chance. Eggs and nestlings may be taken by snakes, including blue racers (Coluber constrictor), rat snakes (Elaphe species), common garter snakes (Thamnophis sirtalis), kingsnakes (Lampropeltis species) and pigmy rattlesnakes (Sistrurus miliarus). Mammalian nest predators include striped skunks (Mephitis mephitis), raccoons (Procyon lotor), weasels (Mustela species), ground squirrels (Spermophilus species), foxes (Vulpes species), domestic cats (Felis catus), feral pigs (Sus scrofa), and armadillos (Dasypus novemcinctus). Adults may be taken by various hawks and are regularly preyed on by loggerhead shrikes (Lanius ludovicianus). (Vickery, 1996)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Savannah sparrows may be dominant over grasshopper sparrows where they co-occur. Grasshopper sparrow nests are sometimes parasitized by brown-headed cowbirds (Molothrus ater). Habitat may influence exposure to nest parasitism, with grasshopper sparrow nests closer to forest edge being more vulnerable. Shiny cowbirds (Molothrus bonariensis) have colonized the Florida range of grasshopper sparrows recently and may parasitize nests. (Vickery, 1996)

Grasshopper sparrows are parasitized by nasal mites (Ptilonyssus sairae), Gulf Coast ticks (Amblyoma maculatum), and bird ticks (Haemaphysalis chordeilis). (Vickery, 1996)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Grasshopper sparrows are a unique element of the native North American grassland fauna.

Economic Importance for Humans: Negative

There are no known adverse effects of grasshopper sparrows on humans.

Conservation Status

Grasshopper sparrow populations have been experiencing declines of 3.9% on average throughout the 20th and into the 21st centuries. Declines are mainly the result of loss and fragmentation of grassland habitats, such as native prairies and pastures. Over 99% of native prairies have been converted to agriculture in Wisconsin, Illinois, and Minnesota. They are considered "least concern" by the IUCN because they are widespread and populations remain large, but they are rare in portions of their range. They are considered a species of special concern in Michigan, California, Washington, New York, Massachusetts, and Wyoming. They are considered threatened in New Jersey, threatened as A. s. floridanus in Florida, and endangered in Connecticut. Prescribed burning, grazing, and mowing have been used to improve habitats for grasshopper sparrows in some areas. (Vickery, 1996)

Most declines have been documented in the subspecies A. s. pratensis, distributed throughout much of the northeastern United States, and A. s. perpallidus, found in the Pacific states, with declines up to 69% since the 1960's. Ammodramus savannarum pratensis populations have been lost from much of their former New England range. The Florida subspecies, A. s. floridanus, now breeds in a much more restricted area than it did formerly. (Vickery, 1996)

Other Comments

Grasshopper sparrows are considered closely related to South American grassland sparrows (Myospiza humeralis) and yellow-browed sparrows (Myospiza aurifrons). (Vickery, 1996)

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.

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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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cooperative breeder

helpers provide assistance in raising young that are not their own

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.

insectivore

An animal that eats mainly insects or spiders.

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.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

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

polygynous

having more than one female as a mate at one time

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

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

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

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

Vickery, P. 1996. Grasshopper Sparrow (Ammodramus savannarum). Birds of North America Online, 239: 1-20. Accessed May 21, 2009 at http://bna.birds.cornell.edu/bna/species/239.

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