Habitat and landscape effects on abundance of Missouri's grassland birds

Authors

  • Robert B. Jacobs,

    Corresponding author
    1. Missouri Department of Conservation, 2901 West Truman Boulevard, Jefferson City, MO 65109, USA
    • Missouri Department of Conservation, 2901 West Truman Boulevard, Jefferson City, MO 65109, USA.
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  • Frank R. Thompson III,

    1. Northern Research Station, U. S. Forest Service, 202 Natural Resources Building, University of Missouri, Columbia, MO 65211-7240, USA
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  • Rolf R. Koford,

    1. U.S. Geological Survey, Iowa Cooperative Fish and Wildlife Research Unit, Science Hall II, Iowa State University, Ames, IA 50011, USA
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  • Frank A. La Sorte,

    1. Department of Fisheries and Wildlife Science, 302 Natural Resources Building, University of Missouri, Columbia, MO 65211, USA
    Current affiliation:
    1. Cornell Lab of Ornithology, Ithaca, NY 14850, USA.
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  • Hope D. Woodward,

    1. Missouri Department of Conservation, 2901 West Truman Boulevard, Jefferson City, MO 65109, USA
    Current affiliation:
    1. U. S. Forest Service, Orleans/Ukonom Ranger District, Six Rivers National Forest, 1 Ishi Pishi Road, Orleans, CA 95568, USA.
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  • Jane A. Fitzgerald

    1. American Bird Conservancy, 8816 Manchester, Suite 134, Brentwood, MO 63144, USA
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  • Associate Editor: Eric Hellgren

Abstract

Of 6 million ha of prairie that once covered northern and western Missouri, <36,500 ha remain, with planted, managed, and restored grasslands comprising most contemporary grasslands. Most grasslands are used as pasture or hayfields. Native grasses largely have been replaced by fescue (Festuca spp.) on most private lands (almost 7 million ha). Previously cropped fields set aside under the Conservation Reserve Program (CRP) varied from a mix of cool-season grasses and forbs, or mix of native warm-season grasses and forbs, to simple tall-grass monocultures. We used generalized linear mixed models and distance sampling to assess abundance of 8 species of breeding grassland birds on 6 grassland types commonly associated with farm practices in Missouri and located in landscapes managed for grassland-bird conservation. We selected Bird Conservation Areas (BCAs) for their high percentage of grasslands and grassland-bird species, and for <5% forest cover. We used an information-theoretic approach to assess the relationship between bird abundance and 6 grassland types, 3 measures of vegetative structure, and 2 landscape variables (% grassland and edge density within a 1-km radius). We found support for all 3 levels of model parameters, although there was less support for landscape than vegetation structure effects likely because we studied high-percentage-grassland landscapes (BCAs). Henslow's sparrow (Ammodramus henslowii) counts increased with greater percentage of grassland, vegetation height-density, litter depth, and shrub cover and lower edge density. Henslow's sparrow counts were greatest in hayed native prairie. Dickcissel (Spiza americana) counts increased with greater vegetation height-density and were greatest in planted CRP grasslands. Grasshopper sparrow (A. savannarum) counts increased with lower vegetation height, litter depth, and shrub cover. Based on distance modeling, breeding densities of Henslow's sparrow, dickcissel, and grasshopper sparrow in the 6 grassland types ranged 0.9–2.6, 1.4–3.2, and 0.1–1.5 birds/ha, respectively. We suggest different grassland types and structures (vegetation height, litter depth, shrub cover) are needed to support priority grassland-bird species in Missouri. © 2011 The Wildlife Society.

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