Rare Species Guide

  Synonyms

Ammodramus henslowii

  Basis for Listing

The Henslow's Sparrow (Centronyx henslowii) breeds in the eastern half of the United States and overwinters in the Southeast. Across the country, Henslow's Sparrow populations declined by over 68% between 1966 and 1991 (Herkert 1994). In Minnesota, Henslow's Sparrows are a widespread but relatively rare summer resident, predominantly throughout the prairie region of  the state. The species requires uncultivated grasslands and old fields with standing, dead vegetation and a substantial litter layer. Areas used one year may be abandoned the next year if the grass has become too long or too short. Therefore, the Henslow's Sparrow's distribution in the state is sporadic and the extent of its former range is difficult to delineate.

The major cause of the species' decline is habitat loss and degradation resulting from urban sprawl, intensive cultivation, increased frequency of mowing hayfields, and conversion of pastures, hay fields, and old fields to row crops (Herkert et al. 2020). The Henslow's Sparrow was classified as a special concern species in Minnesota in 1984, but its continued decline in the state led to its reclassification as endangered in 1996. Since that time, there has been an increase in records (Pfannmuller et al. 2017; Svingen 1998), particularly from grasslands in western Minnesota. However, uncertainties regarding the ups and downs of Conservation Reserve Program (CRP) grassland acreage, and the effects this can have on Henslow’s Sparrow populations, remains a concern.

  Description

The Henslow's Sparrow is an inconspicuous, secretive bird whose short two-syllable song is easily overlooked. This sparrow's most distinctive feature is its large relatively flat olive-colored head with dark stripes. Its streaked chest, rufous-tinged wings, and short tail are also diagnostic. Henslow’s Sparrows can best be observed when the males sing from the top of a clump of grass, weed stalk, or other exposed song perch.

  Habitat

Henslow's Sparrows breed in grasslands with relatively tall grass, a substantial litter layer, and exposed stalks for singing perches. This can include old fields, native prairie, restored prairie (i.e., planted native grasses), and other grasslands with similar structure. The most important native plant community for the species is southern mesic prairie. Southern dry prairie can be regionally important, though only one specific type, dry hill prairie, has multiple Henslow’s Sparrow occurrences. Dry prairie types having loose sand, or sand-gravel substrates do not seem to be as suitable. Litter depth, vegetation height, and the number of standing, dead herbaceous stems are important components of occupied areas (Herkert 1994). Grasslands over 100 ha (247 ac.) are preferable, though smaller areas of suitable habitat are also used by this species (Herkert 1994).

  Biology / Life History

Henslow's Sparrows have been described as breeding in loose colonies, in which several pairs occupy a small grassland (Hanson 1994); however, individual nesting is not uncommon. Males utilize tall forbs as singing perches and vantage points from which to defend their territories, which are approximately 1 ha (2.5 ac.) in size. Females build nests at the base of grass clumps and often construct runways through the leaf litter for use in escaping predators. Females lay an average of 4-5 eggs and incubate them until they hatch in about 11 days. The young grow quickly and are fed by both the male and female. There is usually time for a pair to raise two broods in a season. Brown-headed Cowbird (Molothrus ater) parasitism of Henslow's Sparrow nests is believed to occur infrequently, as the nests are very difficult to find. More significant causes of nest failure include trampling by cattle and predation by snakes and small mammals (Herkert 1994). During the breeding season, Henslow's Sparrows forage in the litter layer for insects and other small arthropods, as well as seeds.

  Conservation / Management

The grasslands inhabited by Henslow's Sparrows typically require habitat management (or natural disturbance) to maintain their suitability. Because of their need for tall vegetation and a substantial litter layer, Henslow's Sparrows do not occupy heavily grazed areas. Prescribed fire may be necessary at times to restore or improve grassland habitat for this species; however, few birds will use these areas during the first several years after burning. Mowing is compatible with Henslow’s Sparrow habitat if vegetation has enough time to grow to an acceptable height and density by the next breeding season. These management practices, and possibly light grazing, can be combined on a rotational basis to maintain suitable habitat (Herkert 1994). Because Henslow's Sparrows are primarily insectivorous during the breeding season, they may be adversely affected by pesticides (Cooper 2012).

  Conservation Efforts in Minnesota

For many years, Great River Bluffs State Park, in The Blufflands, has supported one of Minnesota’s most consistent, important, and accessible sites for Henslow’s Sparrow. There had been a long, though inconsistent, history of the species elsewhere in southern and western Minnesota; however, none of these other populations have been well studied.

Since 1996, observations of Henslow's Sparrows elsewhere in the state have increased, with breeding season records coming from counties scattered throughout western, central, and southern Minnesota. Of particular interest is the consistent presence of this species in several large tracts of native prairie in western Minnesota. Increased monitoring of these western populations is needed to assess the status of Henslow's Sparrows at these sites.

In recent years, reports of Henslow’s Sparrows have largely remained stable or increased, likely benefitting from continuing planting, restoration, and protection of grasslands through programs like CRP, Conservation Reserve Enhancement Program (CREP), Native Prairie Bank, and on lands owned and managed by the Minnesota DNR (Scientific and Natural Areas, State Parks, Wildlife Management Areas, etc.), the U.S. Fish & Wildlife Service (National Wildlife Refuges, Waterfowl Production Areas, etc.), county agencies, Three Rivers Parks District, and numerous other organizations (e.g., The Nature Conservancy, Pheasants Forever, colleges and universities, etc.). With increased coverage by birders and bird surveyors, it is uncertain how much Henslow’s Sparrow populations have actually increased, versus more observers better documenting what has always been on the landscape.

Many sites that now have persistent populations of Henslow’s Sparrow are a mix of grassland types, ownership, and management, rather than solely CRP. While CRP acreage remains important, sparrow populations in Minnesota likely are not as dependent on CRP as in the past.  If habitat managers effectively maintain suitable grassland cover and structure, this more diverse base of grassland habitat should be better able to continue to provide suitable Henslow’s Sparrow habitat without being susceptible to fluctuations in acreage in a single type of ownership or grassland conservation program.

  Authors/Revisions

Steven P. Stucker (MNDNR), 2025

(Note: all content ©MNDNR)

  References and Additional Information

Bolin, K. E. 1996. A draft plan for Henslow's Sparrow (Ammodramus henslowii) habitat management at O.L. Kipp State Park, Winona County, Minnesota. 9 pp.

Cooper, T. R. 2012. Status assessment and conservation plan for the Henslow's Sparrow (Ammodramus henslowii). Version1.0. U.S. Fish and Wildlife Service, Bloomington, Minnesota. 136 pp.

Hanson, L. G. 1994. The Henslow's Sparrow (Ammodramus henslowii) of Minnesota: population status and breeding habitat analysis. M.S. Thesis, Central Michigan University, Mount Pleasant, Michigan. 39 pp.

Herkert, J. R. 1994. Status of habitat selection of the Henslow's Sparrow in Illinois. Wilson Bulletin 106:35-45.

Svingen, P. 1998. Recent status of the Henslow's Sparrow in Minnesota. Loon 70:153-154.