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

    Long-billed Curlew (Numenius americanus)

    Associated Species: Other species that may use habitat in a similar way and/or respond similarly to threats, management, and conservation activities include Mountain Plover and Horned Lark.

    Distribution: The breeding range extends from south-central British Columbia east to southern Manitoba, south to northern Texas, and west through central New Mexico to as far as central Nevada. In Colorado, the birds breed throughout the eastern plains, with the population concentrated in the southeast.

    Habitat Requirements: Curlews breed in shortgrass and mixed-grass habitats, and occasionally in idle cropland. They prefer short vegetation, generally <30 cm (12 in) and often <10 cm (4 in). After hatching, the adults move the chicks to areas of taller grasses and scattered forbs and shrubs for protection from predators and weather extremes; dense forbs or shrubs are avoided, due to low visibility and difficulty of travel for chicks.

    Proximity to standing water seems to be a necessary feature, even though the birds are rarely seen actually using the water. Birds are often found <400 m (0.25 mi) from standing water, and often much closer. The water is often from human sources (windmill overflow, stock ponds, etc.). As with Mountain Plovers, curlews may be attracted to the low vegetation profile and high insect population associated with livestock near such water sources, rather than an attraction to the water itself. Additionally, the birds frequent areas of moist soils, where prey populations are higher.

    Although curlews prefer to nest close to water, the nest sites must be dry. Some nest sites far from water may have been established when water was present, and the birds return out of site fidelity. Nests are located in areas of low grass height and low grass height diversity. In a Colorado study, average height of the tallest vegetation at nest sites was 11.0 cm (4.3 in), and vegetation cover averaged 72.1% (range 50-95%) (King 1978). They occasionally nest in idle croplands such as wheat stubble.

    Ecology: Curlews arrive in Colorado in April, lay eggs in May, and fledge young by mid June. Most of Colorado's adult birds have left the state by 15 July, leaving only the young-of-the-year birds and migrants from the north, which leave by the end of August. Curlews winter along the California coast, the Baja peninsula, central and southern Texas, and throughout Mexico. They feed on insects (especially grasshoppers, but also beetles and butterflies) and other invertebrates (especially worms, crustaceans, and mollusks), but also take small vertebrates including the eggs and young of other birds. Territory size reported across their range varies from 6 to 14 ha (15-35 ac). Many territories are reused in subsequent years, perhaps by the same individuals.

    Management Issues and Conservation Recommendations: Grasshopper control is detrimental, given the species' dependence on grasshoppers and other invertebrate prey. Adopt Integrated Pest Management practices to retain some populations of the prey species.

    Curlews will not renest if the nest is destroyed. Grazing by sheep in shortgrass reportedly is more detrimental than grazing by cattle, as sheep graze an area more completely and to a shorter height, and their habits of grazing across a broad front and traveling in tight herds results more often in nest destruction. Maintain a landscape mosaic of grassland parcels of different heights and densities to provide habitat for foraging, nesting, and brood-rearing. Protect the area around known nest sites, because birds often reuse the same territories.

    Status and Reasons for Concern: This species has a high conservation need locally and throughout its range. This species is on the national Watch List, indicating a high conservation need throughout its range. This is a CDOW Species of Special Concern, and a Sensitive Species in USFS Region 2. Within the Central Shortgrass Prairie, BBS data show a statistically significant annual rate of decline between 1966 and 1996 (-10.00%; P = 0.02; n = 25 routes). This species is arguably the highest conservation priority in this physiographic area. Long-billed Curlews were present on an average of 15.49% (SE = 2.10) of the BBS routes run in Physiographic Area 36 in Colorado during 1988-1997, at an average abundance of 1.68 (SE = 0.21) 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: Increase the species' distribution and abundance, based upon results from the BBS and MCB monitoring programs.

    Selected References: Allen 1980, Andrews and Righter 1992, Cochran and Anderson 1987, Kingery 1998, McCallum et al. 1977.


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