Passerculus sandwichensis

Geographic Range

Savannah sparrows ( Passerculus sandwichensis ) are native to the Nearctic, Neotropical, and Oceanic Island biogeographic regions, reflecting their broad and diverse distribution. Their range extends from the northern Canadian provinces and Alaska southward to El Salvador. Longitudinally, they occur across the entire North American continent, from Bristol Bay, Alaska, in the west to St. John’s, Newfoundland, in the east.

During the winter months, all populations breeding in Alaska, Canada, and the northernmost regions of the United States migrate to more temperate areas. Their primary wintering grounds include the Great Plains, non-mountainous areas east of the Appalachian Mountains, and regions south of the Rocky Mountains. Wintering populations also occur in parts of the Neotropical region, including the Caribbean islands such as the Bahamas, Belize, the Cayman Islands, and Cuba.

In Mexico, a resident, non-migratory population occupies highland regions within the Nearctic zone, particularly the Trans-Mexican Volcanic Belt and the Sierra Madre Occidental. This population spans from Guanajuato in the north to Morelos in the south, and from Puebla in the east to Jalisco in the west.

Non-migratory populations are also established in the northeastern United States, from Norfolk, Virginia, to the southern tip of Maine, and along the northwestern coast from central California to the Washington State–Canada border. These resident groups persist year-round within localized coastal environments.

Additionally, vagrant individuals have been observed on Oceanic Islands and in overseas territories, with records from Bermuda, Japan, the Republic of Korea, the Azores (Portugal), eastern Siberia (Russian Federation), and the United Kingdom.

• Biogeographic Regions
• nearctic nearctic
  • native native
• neotropical neotropical
  • native native
• oceanic islands oceanic islands
  • native native

Habitat

Savannah sparrows occupy a diverse range of open habitats, including grasslands, marshes, agricultural fields, coastal meadows, and highland plains. Habitat vary among populations, with migratory individuals breeding in temperate grasslands and tundra, while resident, non-migratory populations persist in specific regions year-round.

During the winter months, migratory populations utilize similar open habitats, including salt marshes, coastal prairies, and inland grasslands. Although Savannah sparrows are mainly terrestrial, they may also be found in wetland environments, including marshes and riparian areas, particularly during migration and the non-breeding season. Habitat selection is strongly influenced by the availability of low vegetation for nesting and cover, as well as open ground for foraging. Some of these areas are at elevations as low as sea level.

In central Mexico, non-migratory population primarily inhabits the high-altitude grasslands of the Trans-Mexican Volcanic Belt and Sierra Madre Occidental, which are at elevations ranging from 1,500 to 4,500 meters, with a typical elevation between 2,000 and 3,000 meters. These populations are commonly found in open fields, shrublands, and disturbed habitat such as pastures and cultivated land.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial
• freshwater freshwater

• Terrestrial Biomes
• tundra tundra
• savanna or grassland savanna or grassland
• chaparral chaparral
• scrub forest scrub forest
• mountains mountains

• Wetlands
• marsh marsh

• Other Habitat Features
• suburban suburban
• agricultural agricultural
• riparian riparian

Physical Description

Savannah sparrows are small, compact birds with short, notched tails and small, conical bills. They measure between 11 and 15.5 cm in length, with wingspans ranging from 19 to 23 cm. They weigh between 15 and 28 grams. This species is sexually monomorphic in plumage, meaning males and females look alike; however, males tend to be slightly larger on average, though specific measurement comparisons between the sexes are limited.

Feather patterns include brown streaks, giving them a distinctive appearance. Across most of their range, they have a pale beige median crown stripe, though this feature is absent in some salt marsh populations. Their eyebrow stripe is typically yellow at the front anteriorly but may appear beige in some individuals. A thin, dark malar stripe is present, and their remiges and rectrices are brown without white markings. They lack distinct wing bars, but a small yellow patch is often visible at the bend of the wing. Their throats, breasts, and bellies range from whitish to pale beige, with brown streaks on the breast that may form a small central spot. The throat and belly may be either streaked or clear. Their legs are pinkish to horn-colored, and they have brown irises.

Juveniles resemble adults but have heavier streaking on the breast, more rufous tones on the wings and tail, and little to no yellow in the eyebrow stripe. Their overall coloration is generally buffier, and they tend to have a less distinct crown stripe. The lower mandible is paler than the upper, and their tails are slightly forked.

Savannah sparrows are often compared to species in the closely related genus Melospiza , such as song sparrows ( Melospiza melodia ) and Lincoln's sparrows ( Melospiza lincolnii ). Members of the genus Melospiza generally exhibit longer tails, more rounded wings, and more heavily streaked plumage overall, especially on the underparts. Additionally, Melospiza species tend to have slightly heavier bills and lack the yellow eyebrow marking characteristic of most Savannah sparrows.

These combined features, especially the presence of yellow near the lores, compact body shape, and fine streaking make Savannah sparrows distinguishable from other sparrows within the same family.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike
• male larger

Development

Savannah sparrows, like all birds, exhibit determinate growth, and sex is determined genetically with Z or W chromosomes.

After mating, females lay 3 to 6 eggs in a well-hidden grass, rootlets, and hair-lined nest on the ground. The eggs are incubated for 10 to 13 days, primarily by the females. During this time, the embryo develops inside the egg, which is nourished by the yolk. The eggs of Savannah sparrows are primarily light in color, ranging from pale white to shades greenish or blueish. Their eggs are typically spotted in a variety of darker colors from red to gray and even brown. Savannah sparrow eggs are noted for their shiny and smooth appearance.

Hatchlings are altricial, meaning they hatch blind, featherless, and completely dependent on parental care. The hatchlings grow rapidly and start developing their feathers. Nestlings remain in the nest for 8 to 13 days before fledging. As nestlings, they open their eyes, their down feathers are replaced by juvenile plumage, and they strengthen their wings and legs. At the fledgling stage, young Savannah sparrows stay close to their parents, who continue feeding them until they learn to forage on their own. This stage lasts a couple of weeks as the young birds refine their flying and survival skills.

Savannah sparrows initially exhibit juvenile plumage. After their first molt, they start resembling adults. Savannah sparrows reach sexual maturity at about age 1 and exhibit adult plumage and behaviors, including territoriality and courtship displays.

Reproduction

Savannah sparrows display both monogamous and polygynous mating systems. When breeding in northern regions with shorter seasons, males and females form monogamous pairs. The short months of the tundra breeding season and the necessity of male parental care contribute to the need of monogamy in northern regions. In more southern populations, males will mate with multiple females. The proportion of polygynous males varies annually and regionally, ranging from 15% to 43% across studies. Factors such as territory quality and resource distribution influence the occurrence of polygyny.

Males attract females through song displays. Males perch on shrubs, trees, or fence posts to establish territory boundaries. Males actively defend their territories through different displays and chases to deter rival males, ensuring exclusive access to resources and potential mates within their area.

The mating system influences the social structure and parental roles within Savannah sparrow populations. In monogamous pairs, both parents share duties such as, building the nest, egg incubation, and feeding and fostering their offspring. In polygynous systems, where males have multiple mates, males provide less paternal care to their offspring. Females in these systems provide practically all the care for their offspring, which reduces their reproductive success.

• Mating System
• monogamous monogamous
• polygynous polygynous

The reproductive cycle of Savannah sparrows is closely tied to seasonal changes, with breeding typically occurring between April and August. This period aligns with warmer temperatures and greater food availability, which supports successful nesting. Savannah sparrows are iteroparous, meaning they can breed multiple times throughout their lives.

Within a single breeding season, they produce 1 to 3 broods. Females lay between 3 and 6 eggs per clutch, with typically 4 to 5 eggs. The eggs are incubated primarily by the females for 10 to 13 days (average = 12 days). Once hatched, hatchlings weigh around 1 to 3 g (average = 2 grams), and the altricial chicks are blind, featherless, and entirely dependent on parental care. Both parents participate in feeding and protecting the young.

Fledging occurs 8 to 11 days after hatching, most often at 9 days. Even after leaving the nest, young Savannah sparrows remain dependent on their parents for an additional 14 to 21 days while they learn to forage and evade predators.

Savannah sparrows reach sexual maturity within their first year, typically by the age of 9 to 12 months. Like all birds, they mate using internal fertilization and are oviparous.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• oviparous oviparous

Savannah sparrows exhibit parental investment from both parents, with a more prominent role played by females. Particularly in southern populations where polygamy is found and there is little to no parental investment by males.

In northern regions where monogamous pairs are formed, pre-fertilization parental investment is in the form of the females production of healthy eggs and the female's ability to find safe and suitable nesting sites in preparation for breeding. The males parental investment at this stage is mainly defending resource rich territories.

Pre-hatching parental investment is predominantly the females responsibility as she is the main constructor of the nest, and they are the main incubators of egg for 10 to 13 days. Males during this stage help by provisioning the female with food, defending their territory and occasionally incubating the eggs.

Post-hatch parental investment reaches its peak due to the altricial nature of the hatchlings. Both parents help feed and protect their offspring, females often take the lead in brooding. This behavior helps the young maintain body heat and shields them from environmental hazards. This stage typically lasts 8 to 13 days.

Pre-independence both parents will continue to provision their young while teaching skills such as foraging and predator recognition. Post-independence juveniles remain in close proximity of their parental territories for a few weeks before fully dispersing.

• Parental Investment
• altricial altricial
• male parental care male parental care
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • male
    • 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

Lifespan/Longevity

Savannah sparrows in the wild can live up to 6.5 years. The oldest individual in captivity lived to at least 18 years. Their expected life spans in captivity is 12 years and 5 years in the wild.

Factors that limit lifespan in the wild include predation, extended periods of precipitation, and loss of habitat. Annual adult survival rates are between 28%-42%.

Behavior

Savannah sparrows are semi-social birds and are usually a part of loose flocks in the non-breeding season. During the breeding season, males become territorial and defend their territory through songs and other displays.

Savannah sparrows are migratory birds that move south from September to October. They migrate nocturnally. These sparrows return to breeding grounds in the spring, and arrival time is later at more northern latitudes. For example, they reach breeding grounds in Kentucky in February. In March, they arrive in Missouri and southern Canada. In April, they reach South Dakota and Nova Scotia, Canada. Finally, by early May, they arrive in Alaska. Males typically arrive at breeding grounds one week prior to potential mates.

Savannah sparrows have distinct flight patterns which are short, with flights that are close to the ground. They are also cursorial and walking and running through grasslands rather than flying. They are diurnal which means they are active during the day.

There is no strong evidence of a social hierarchy among Savannah sparrows based on territory during breeding seasons. Outside their breeding season, these birds forage in mixed-species flocks and communicate through songs and other displays.

• Key Behaviors
• cursorial
• terricolous
• flies
• diurnal diurnal
• motile motile
• migratory migratory
• territorial territorial
• social social

Home Range

Home ranges for Savannah sparrows during the breeding season average 5,000 square meters (range 2500 to 10000 m^2). The range is dependent on population density and the overall quality of their habitat. Males are territorial and exhibit fighting and defensive behaviors. They can chase one another for up to 200 m away from the nesting area, although the territory size has not been quantified. They fight most early in the breeding season when pairs are first getting established. Later in the season, males revert to less aggressive displays (quivering, alarm calls, wing-hits just off the ground).

Communication and Perception

Savannah sparrows rely on acoustic communication, with males singing to attract mates and mark their territory. Short calls help them stay in contact and signal danger. Numerous studies are currently being conducted on the songs of the Savannah sparrow, examining how variations in tone and pitch influence their meaning. Males have intricate songs that last 2 to 3 seconds. They start with several distinct high-pitched chips and trail into a buzzy sound at 7.2 kHz. It's described as insect-like. The song descends briefly with a few cleared, lower-kHz (4.4 kHz) notes at the end. Although only males can create songs, both sexes can make less complicated alarm calls and nestlings can make simple begging calls.

In addition to vocalizations, they use visual signals like different body postures and wing movements during courtship and territorial defense. These sparrows have tactile behaviors, such as grooming, reinforce bonds between mates and the kin between parents and chicks. They establish territories by visual displays plus tactile wing-tapping and jumping just off the ground to fight.

Their visual and acoustic senses are advanced, allowing them to detect predators, locate food, and interact socially.

Xu et al. (2021) suggest that most songbirds use a magnetic compass in migratory routes.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical
• magnetic magnetic

Food Habits

Savannah sparrows are omnivorous birds that consume both plants and animals. During the breeding season, their diet consists mainly of insects and other small invertebrates, classifying them as insectivores. These birds feed on a variety of arthropods, including grasshoppers (Order Orthoptera), beetles (Order Coleoptera), caterpillars (Order Lepidoptera), flies (Order Diptera), and spiders (Order Araneae).

In colder months, they shift toward a granivorous diet, relying more on grains and seeds for sustenance. In these months, they consume seeds from different grasses and forbs, such as ( Panicum ), ragweed ( Ambrosia ), and foxtail ( Setaria )

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods
• herbivore herbivore
  • granivore granivore
• omnivore omnivore

• Animal Foods
• terrestrial non-insect arthropods

• Plant Foods
• seeds, grains, and nuts

Predation

Savannah sparrows possess cryptic adaptations which affect their distinctive coloration. These sparrows hide in grasslands and possess brown and beige streaked plumage to blend into their surrounds. Savannah remains low to the ground and freezes in place when threatened. If detected, they employ swift, erratic flight patterns in short bursts to evade predators.

During early stages of their life, Savannah sparrows are venerable to snakes and foxes such as eastern racer snakes ( Coluber constrictor ) and red foxes ( Vulpes vulpes ). As adults, Savannah sparrows face threats from predators such as red-tailed hawks ( Buteo jamaicensis ), domestic cats ( Felis catus ), and short-eared owls ( Asio flammeus ).

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Savannah sparrows play important roles in their ecosystems, primarily through being prey for larger birds and consuming insects and seeds.

Brown-headed cowbirds ( Molothrus ater ) are brood parasites that rely on Savannah sparrows to raise their young; this parasitism can impact the reproductive success of Savannah sparrows.

Ectoparasites include blowflies ( Protocalliphora hirudo ), which are rare but can affect a small percentage of nestlings. Louse flies in the family Hippoboscidae were found in fledglings at rates of 10%. Adults may rarely host ticks of unreported species.

Protozoal parasites ( Plasmodium ) are endoparasite blood protozoans that cause avian malaria. prevalence varies widely among Savannah sparrow populations, with infection rates ranging from 0% to 60% across 14 studied groups. Infections are more frequently observed in mainland males and are associated with increased sexual size dimorphism, suggesting a possible a possible role of parasite-mediated sexual selection.

Economic Importance for Humans: Positive

Savannah sparrows serve as a small part of the large bird watching industry that generates around $108 billion annually across the United States. Local economies benefit economically through guided bird watching tours and other ecotourism activities.

• Positive Impacts
• ecotourism ecotourism

Economic Importance for Humans: Negative

There are no known adverse economic effects of Savannah sparrows on humans.

Conservation Status

Savannah sparrows are listed as "Least Concern" on the IUCN Red List. They are protected under the United States Migratory Bird Treaty Act, which makes it illegal to kill, take or have possession of any migratory bird. While the species is not listed as a whole under the Endangered Species Act, there are some subspecies that have protections. Passerculus sandwichensis beldingi is a subspecies that inhibits coastal salt marshes in California is listened as an endangered species. Passerculus sandwichensis princeps inhabits Sable Island, Nova Scotia and is designated as "Special Concern" by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).

The primary threats to vulnerable subspecies, such as Passerculus sandwichensis beldingi , stem from habitat loss, particularly the destruction of coastal salt marshes for development and agricultural expansion. These habitats are essential for nesting and foraging. Similarly, individuals in the subspecies Passerculus sandwichensis princeps face substantial risks due to storm exposure and shoreline erosion in their breeding areas. Passerculus sandwichensis princeps in Manitoba declined 77% in 25 years, largely due to habitat altercations.

Other threats documented include mowing practices in agricultural fields and at airports. Hay fields can result in up to 99% nest failure, this is due to fledging times occurring around June 21st which is optimal mowing days. Airports offer great grassland habitats which are suitable for Savannah sparrows, but due to mowing regimes their results are often high nest failure.

To safeguard Savannah sparrows and their vulnerable subspecies, several protections have been in place. At the Federal level Savannah sparrows are protected under the Migratory Bird Treaty Act, which prohibits the capturing, possession or killing of Savannah sparrows without proper authorization. For subspecies at greater risk, such as Passerculus sandwichensis beldingi , listing under the Endangered Species Act ensures targeted conservation efforts, including habitat preservation and restoration initiatives in California’s coastal salt marshes. Similarly, Passerculus sandwichensis princeps , designated as a species of Special Concern by COSEWIC in Canada, benefits from monitoring programs and conservation planning aimed at minimizing habitat degradation from storm impacts and shoreline erosion. Additionally, land management practices are being adjusted in some areas such as delaying mowing during nesting season to reduce nest failure.

Additional Links

Encyclopedia of Life

Contributors

Alec Correa (author), Radford University, Natalie May (editor), Radford University, Alexander McVicker (editor), Radford University, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

BGFG, 2025. "The Surprising Economic Impact of Birdwatching in the U.S" (On-line). BirdWatching. Accessed April 01, 2025 at https://www.birdwatchingdaily.com/beginners/birding-faq/the-surprising-economic-impact-of-birdwatching-in-the-us/ .

Bedard, J., J. McNeil. 1979. Protocalliphora hirudo (Diptera: Calliphoridae) infesting Savannah sparrow, Passerculus sandwichensis, (Aves: Fringillidae), in eastern Quebec. Canadian Entomologist , 111/1: 111-112.

BirdLife international, 2021. "Passerculus sandwichensis" (On-line). The IUCN Red List of Threatened Species 2021: e.T103780243A138559631. Accessed February 03, 2025 at https://dx.doi.org/10.2305/IUCN.UK.2021-3.RLTS.T103780243A138559631.en. .

COSEWIC, 2023. "Savannah Sparrow princeps subspecies (Passerculus sandwichensis princeps): COSEWIC rapid review of classification 2023" (On-line). Government of Canada. Accessed April 01, 2025 at https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/savannah-sparrow-2023.html. .

Dixon, C. 1978. Breeding biology of the savannah sparrow on Kent Island. The Auk , 95/2: 235-246.

Gomez, E., J. Garcia, G. Estefania, V. Vazquez, R. Castillo, I. Ortega. 2024. The Savannah sparrow (Passerculus sandwichensis). The Southwestern Naturalist , 69/1: 1-6.

Harrison, C. 1978. A Field Guide to Nests, Eggs, and Nestlings of North American Birds . Cleveland, Ohio: Collins Press.

Headstrom, R. 1970. A Complete Field Guide to Nests in the United States (including those of Birds, Mammals, Insects, Fishes, Reptiles, and Amphibians) . New York, New York: Van Rees Press.

Miller, C., L. McEwen. 1995. Diet of nesting savannah sparrows in interior Alaska (dieta de Passerculus sandwichensis anidando en el interior de Alaska). Journal of Field Ornithology , 66/1: 152-158.

Reed, C. 1965. North American Birds Eggs . New York, New York: Dover Publications, Inc.

Rising, J. 1988. Geographic variation in sex ratios and body size in wintering flocks of Savannah sparrows (Passerculus sandwichensis). The Wilson Bulletin , 100/2: 183-203.

Rising, J. 2000. Geographic variation in size and shape of Savannah sparrows (Passerculus sandwichensis). Studies In Avian Biology , 23/12: 1-65.

Sharma, S., S. Dobney, R. Norris, S. Doucet, A. Newman, J. Burant, I. Moran, S. Mueller, H. Spina, D. Mennill. 2024. Effects of age, breeding strategy, population density, and number of neighbors on territory size and shape in Passerculus sandwichensis (Savannah sparrow). Ornithology , 141/4: ukae025. Accessed February 03, 2025 at https://doi.org/10.1093/ornithology/ukae025 .

Sung, H., P. Handford. 2020. Song characters as reliable indicators of male reproductive quality in the Savannah sparrow (Passerculus sandwichensis). Canadian Journal of Zoology , 98/1: 32-38.

Wells, J., K. Rosenberg. 1999. Grassland bird conservation in northeastern North America. Studies In Avian Biology , 19: 72-80.

Wheelwright, N., J. Rising. 2020. "Savannah sparrow  (Passerculus sandwichensis), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA." (On-line). Accessed February 03, 2025 at doi: 10.2173/bow.savspa.01 .

Wheelwright, N., C. Schultz. 1994. Age and reproduction in savannah sparrows and tree swallows. Journal of Animal Ecology , 63/3: 686-702.

Wheelwright, N., J. Templeton. 2003. Development of foraging skills and the transition to independence in juvenile Savannah sparrows. The Condor , 105/2: 279-287.

Xu, J., L. Jarocha,, T. Zollitsch, 33 more authors. 2021. Magnetic sensitivity of cryptochrome 4 from a migratory songbird. Nature , 594: 535–540.