Grasshopper Sparrow (Ammodramus savannarum)
Associated Species: Other species that may use habitat in a similar way and/or respond similarly
to threats, management, and conservation activities include Vesper Sparrows in migration and
Upland Sandpiper and Western Meadowlark during the nesting season.
Distribution: Grasshopper Sparrows breed in grasslands from southern British Columbia east to
southern Maine, south to central Florida, and west to northern Sonora. In Colorado, they nest
throughout the eastern plains, with highest concentrations in the northeast and near the South
Platte and Arkansas rivers.
Habitat Requirements: These sparrows use most types of grassland, especially tallgrass and
midgrass, but also shortgrass where shrubs or tall forbs are present. In addition to native
grasslands, they will nest in CRP lands planted to taller grasses and may be heavily reliant on these
in the shortgrass region. Grasshopper Sparrows require some areas of bare ground since they
forage on the ground; however, it is unclear how much they need, as studies have described bare
ground cover in territories as ranging from 2% to 34%. In general, they prefer sites where much
of the vegetation is >10 cm (4 in) high. They are highly territorial, and require the presence of tall
forbs, scattered trees, or shrubs for singing perches; however, they avoid areas with more than
35% shrub cover.
Ecology: Grasshopper Sparrows arrive in Colorado in mid May and remain through September.
They initiate nesting in early June, and most young fledge by the end of July. They winter across
the southern tier of states, south into Central America. They eat mostly insects, especially
grasshoppers, but also other invertebrates and seeds.
Management Issues and Conservation Recommendations: Grasshopper Sparrow populations
in a particular location can vary widely from year to year, as the birds move around in response to
changes in their habitat. This tendency is reinforced by its semi-colonial nesting habits.
Encourage public land managers and private landowners to provide a landscape mosaic of
grassland parcels of different structural stages to provide Grasshopper Sparrow populations
with options for establishing breeding grounds in any given year.
Grasshopper Sparrows are considered a grassland-interior species. In several studies, including
some in Colorado, breeding populations were more abundant in areas distanced from other land-use types, such as suburban developments, recreational trails, and cropland (Vickery 1996).
Provide suitable habitat in patches large enough--at least 12 ha (30 ac)--to accommodate
Grasshopper Sparrow populations usually respond negatively to grazing or burning in areas where
grasses are already comparatively short and sparse (Saab et al. 1995), due to loss of needed nest
cover and song perches. In some areas, vegetation requires several growing seasons to recover to
conditions suitable to this species. Graze lightly or not at all in areas of short, sparse grasses.
Burn grassland parcels in rotation, such that some unburned habitat is always available.
Mowing operations in hayfields often destroy nests or exposes them to predators. Delay mowing
until after the completion of nesting, i.e., until late July.
Status and Reasons for Concern: This species has a moderately high conservation need
throughout its range, high representation in the physiographic area (14.8% of the total
population), and a declining population trend. Within the shortgrass physiographic area, BBS
data show a statistically significant annual rate of decline between 1966 and 1996 (-2.6%; P =
0.09; n = 54 routes). BBS data also show a significant annual rate of decline survey-wide for the
same period (-3.6%; P < 0.01; n = 1404 routes). Grasshopper Sparrows were present on an
average of 70.98% (SE = 1.88) of the BBS routes run in Physiographic Area 36 in Colorado
during 1988-1997, at an average abundance of 21.05 (SE = 1.31) individuals per route. The
mean number of routes run each year was 29.2 (SE = 2.28). This species is monitored by MCB
with point transects.
Biological Objective: Maintain or increase the species' distribution and abundance, based upon
results of the BBS and MCB monitoring programs.
Selected References: Andrews and Righter 1992; Bock and Webb 1984; Bock et al. 1992, 1993;
Kingery 1998; Vickery 1996.