Land Bird Conservation Plan Colorado  

Introduction
Overview of Colorado
Physiographic Region 36

  • Grasslands
  • Lowland Riparian
  • Shore/Bank
  • Wetlands


  • Physiographic Region 62
    Physiographic Region 87
    Implementation Strategies
    Literature Cited
    Appendices

    Physiographic Region 36: Central Shortgrass Prairie

    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 breeding birds.

    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.


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