Grasshopper sparrows (Ammodramus savannarum) are small sparrows that inhabit grasslands across much of North America. Their preferred habitat consists of large fields and prairies with patches of bare ground and short, sparse vegetation. Grasshopper sparrows get their name from their insect-like song that sounds like a grasshopper call. They are cryptically colored brown, gray, and buff birds that can be difficult to see as they forage on the ground for seeds and insects in dense grasses. Knowing the geographic distribution and habitat requirements of grasshopper sparrows can help us better understand and conserve these increasingly threatened birds.
Grasshopper Sparrow Range
Grasshopper sparrows generally breed across the central and eastern United States and Canada. Their breeding range stretches from southeastern British Columbia across to southern Ontario and Quebec, south throughout the Great Plains, Midwest, and eastern states to northeastern Mexico. The grasslands of the Midwest form the core of their breeding grounds. Some isolated breeding populations exist west of the Cascades in Oregon and Washington and in the desert grasslands of Arizona and New Mexico.
Grasshopper sparrows overwinter primarily along the coasts of the southeastern United States, including parts of North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Louisiana, and Texas. They can also be found overwintering in small numbers on the lower Pacific coast and interior Mexico.
There are several geographic subspecies of grasshopper sparrow across their large range. The eastern grasshopper sparrow (A. s. pratensis) breeds east of the Appalachian Mountains. The Florida grasshopper sparrow (A. s. floridanus) is an endangered subspecies limited today to very small remnants of Florida dry prairie. The Henslow’s sparrow (A. s. henslowii) of the Northeast and Midwest was previously considered a separate species but is now classified as a subspecies.
Breeding Habitat
During the breeding season, grasshopper sparrows prefer large fields and dry grasslands with patchy bare ground. They favor native grasslands, pastures, hayfields, grassy meadows, open disturbed areas, and grasslands within pine savannas and shrublands. Nesting areas generally have sparse, patchy, short-to-moderate height vegetation, often with scattered low woody vegetation. Bare ground space is an important feature of quality breeding habitat.
Typical vegetation height in breeding areas ranges from 1 to 12 inches (2.5-30 cm). Grasshopper sparrows avoid fields of dense, uniformly tall vegetation because it prevents them from walking and hopping on the ground while foraging. They will inhabit crop fields, such as alfalfa, oats, corn, or wheat, but only if the vegetation is short and patchy. Patches of bare ground greater than 6-8 inches (15-20 cm) across are utilized for dust bathing and foraging for insects and seeds.
Key Elements of Breeding Habitat
- Large grassland areas >30 acres (>12 hectares)
- Sparse, patchy grasses and forbs 1-12 inches (2.5-30 cm) tall
- Scattered bare ground patches >6 inches (15 cm) across
- Scattered low shrubs
Territories may contain small patches of woody vegetation, but grasshopper sparrows avoid nesting within or near dense shrub cover or woodlands. They require expansive open grasslands away from trees, showing a preference for grassland patches larger than 30 acres (12 hectares). Territory sizes range from 2-5 acres (0.8-2 hectares) per pair.
Wintering Habitat
On their wintering grounds along the Gulf Coast and southeastern Atlantic Coast, grasshopper sparrows inhabit open grassy areas including wet grasslands, cattle pastures, fallow fields, citrus groves, open pine woods, and airports. They prefer sites with bare ground and low vegetation less than 12 inches (30 cm) high. Winter flocks often mix with other open country sparrows.
Migration and Vagrancy
Grasshopper sparrows migrate at night to and from their breeding and wintering grounds. Peak spring migration occurs in April and May. Fall migration peaks in late August to mid-September. Some western birds may migrate southward east of the Rocky Mountains before traveling south to their Gulf Coast wintering areas.
Vagrant grasshopper sparrows sometimes wander outside the normal breeding range, showing up in atypical grassland, meadow, and open agricultural habitats across North America. Vagrants have been sighted west to California, Oregon, Washington and British Columbia and north to various parts of Canada.
Population Status and Threats
Grasshopper sparrow numbers have declined significantly in recent decades primarily due to loss of grassland nesting habitat. Breeding Bird Survey data indicates population declines of 2-3% annually from 1966 to 2015 resulting in an estimated 65% overall decline. The North American Breeding Bird Survey estimated the global breeding population at 5.5 million birds in 2015.
Habitat loss is the greatest threat to grasshopper sparrows. Conversion of native grasslands to agriculture and tree plantations has greatly reduced available breeding habitat. Land management practices including fire suppression and livestock overgrazing also degrade remaining grasslands. Haying operations and early mowing can destroy nests. Pesticide use reduces insect prey. Urban and suburban development continues to consume grasslands.
Climate change may also threaten some populations through increased droughts and changing precipitation patterns in the Great Plains. However, if climate change increases disturbed open habitats such as grasslands, it may benefit the species. Conservation of remaining grasslands through private landowner incentives, conservation easements, and protections on public lands is critical to maintaining grasshopper sparrow populations.
Interesting Facts
- The grasshopper sparrow’s insect-like song is more complex and melodious than a straightforward grasshopper call. Males sing from fence posts and low perches.
- They get their name not just from their song, but also from their preference for habitats with many grasshoppers, a primary food source.
- While foraging, grasshopper sparrows typically stay low, walking or hopping on the ground while picking insects and seeds. This can make them very difficult to observe.
- To avoid predators, nests are well-hidden in thick clumps of grass, often with a domed roof over the nest entrance.
- Grasshopper sparrow numbers appear to fluctuate cyclically every 9-10 years, possibly related to changing precipitation and vegetation conditions.
- Some grasshopper sparrows migrate long distances while others may remain year-round on breeding grounds in the southern part of their range.
Conclusion
Grasshopper sparrows thrive in expansive open grasslands across central North America but face severe threats from habitat loss. Conservation of existing prairies and grassy agricultural lands is crucial for maintaining populations of this wary sparrow into the future. Providing large tracts of suitable habitat with bare ground, sparse low vegetation, and grasshopper prey sources offers the best opportunity for reversing population declines.
Understanding the geographic distribution, migratory patterns, and very specific habitat requirements of grasshopper sparrows can help inform land management decisions and habitat restoration efforts. With proper management focused on maintaining and expanding grassland habitats, grasshopper sparrows may continue to sing their insect-like songs from fence posts for years to come.