Woody Vegetation Removal Benefits Grassland Birds on Reclaimed Surface Mines

Grassland birds have declined throughout North America. In the midwestern United States, reclaimed surface mines often provide expanses of contiguous grassland that support grassland birds. However, some reclaimed surface mines often experience severe woody vegetation encroachment, typically by invasive trees and shrubs, including black locust Robinia pseudoacacia, autumn olive Elaeagnus umbellata, and bush honeysuckle Lonicera spp. We conducted point-count surveys to investigate the effects of woody canopy cover and response to treatments of woody vegetation on the abundance of birds. Our treatments were a control, an herbicide application, and an herbicide application followed by cutting and shredding of standing dead woody vegetation. Estimated density of eastern meadowlark Sturnella magna, grasshopper sparrow Ammodramus savannarum, and Henslow's sparrow Centronyx henslowii was 670%, 958%, and 200%, respectively, greater on areas treated with herbicide and shredding and 279%, 666%, and 155%, respectively, greater on areas treated with herbicide-only when compared with control sites. When woody canopy cover increased from 0% to 20%, densities of eastern meadowlark, grasshopper sparrow, and Henslow's sparrow decreased by 83.9%, 74.9%, and 50.7%, respectively. Conversely, densities of eastern towhee Pipilo erythrophthalmus, prairie warbler Setophaga discolor, yellow-breasted chat Icteria virens, and yellow warbler Setophaga petechia increased 67.4%, 57.0%, 34.6%, and 117.7%, respectively, as estimated woody canopy coverage increased from 20% to 60%. Our results showed treating encroaching woody vegetation on reclaimed surface mines with herbicide and shredding increases available habitat used by grassland birds. Maintaining grasslands on reclaimed surface mines at ≤10% woody canopy coverage would be most beneficial to eastern meadowlarks, grasshopper sparrows, and Henslow's sparrows.

Seed Preferences of Wintering Henslow's Sparrows

Abstract. The Henslow's Sparrow (Ammodramus henslowii), a species of conservation concern, winters primarily in longleaf pine (Pinus palustris) forest ecosystems in the southeastern U.S. These pine savannas have been reduced to 5% of their former range, with remaining patches requiring active management with fire to maintain characteristic structure and plant diversity. Wintering Henslow's Sparrow abundance tracks growing-season fires; bird abundance peaks in the winter following burning, then declines in subsequent winters. Fire also determines dominant plant species, suggesting that Henslow's Sparrows may respond to abundance of preferred seeds. To determine diet preferences of Henslow's Sparrows, we tested seeds from eight species of native plants from southeastern Louisiana pine savannas, including species common in the first winter after burning (‘fire grasses’) and species that increase in abundance in the second and subsequent winters after burning. Seed consumption by individual birds differed considerably, suggesting that Henslow's Sparrows forage on a variety of resources in the highly diverse savannas. Henslow's Sparrows preferred fire grasses, especially Muhlenbergia expansa (cutover muhly). They also preferred Dichanthelium angustifolium (needleleaf rosette grass), a species more common in the second year after burning, but consumed relatively little of the sedges Rhynchospora plumosa (plumed beaksedge) and R. gracilenta (slender beaksedge), species common in the second winter after fire. Birds consumed almost none of the ubiquitous grass Schizachyrium scoparium (little bluestem). These results suggest that preferred seeds may include those that are most common in the first winter after burning, but that some suitable seeds are available for at least another winter.