Habitat associations of grassland and shrubland bird communities at reclaimed surface-mines in Southern Illinois

The grassland bird-community has declined significantly in abundance and diversity in Illinois over the past century. Reclamation of surface coal-mines in southern Illinois has created ca. 50,000 ha of grassland habitat that offers surrogate habitat for grassland and shrubland birds. Much of the grassland habitat created by reclamation of mine lands has not been managed and has succeeded to shrubland habitat dominated by both native and non-native shrubs. The purposes of this research were to identify the bird community utilizing reclaimed surface-mines in southern Illinois, and to examine the habitat-associations of the bird community and compare those to previously reported habitat-associations. I examined bird communities, plant structure and composition, and invertebrate communities at grasslands and shrublands at 3 reclaimed surface-mines in southern Illinois. I used 100-m wide strip-transects to survey the bird community and measured habitat characteristics including: vegetation height and density, litter depth and cover, shrub density and height, and plant composition. I observed 57 bird species over 126 surveys in 2008 and 2009. I used Generalized Linear Models and Akaike's Information Criteria to develop habitat-association models for 7 bird species: Henslow's sparrow (Ammodramus henslowii), grasshopper sparrow (Ammodramus savannarum), eastern meadowlark (Sturnella magna), dickcissel (Spiza americana), indigo bunting (Passerina cyanea), field sparrow (Spizella pusilla), and Bell's vireo (Vireo belli). Of these 7 species, dependable models were found for the Henslow's sparrow, grasshopper sparrow, eastern meadowlark, and field sparrow. The best habitat model for Henslow's sparrows indicated a positive association with % litter cover and a negative association with large variations in grass cover. The best habitat model for grasshopper sparrows indicated a negative association with both litter cover and depth and a positive association with grassland area. The best habitat model for the eastern meadowlark indicated a negative association with visual obstruction and shrub density. The best habitat model for the field sparrow indicated a curvilinear association with shrub density and visual obstruction. The habitat-association model for Henslow's sparrows differed from previous research in that neither vegetation height nor density were indicated as important habitat characteristics. To identify the habitat characteristics that have the greatest effect on the overall bird-community composition, I generated graphical ordinations using non-metric multidimensional scaling. The habitat factors most affecting the bird community composition were: vegetation density, vegetation height, litter depth, shrub density, shrub height, warm-season grass cover, and the ratio of habitat area to perimeter. Invertebrate biomass at a site was positively correlated to forb cover and plant richness and negatively correlated to grass cover. Grassland bird species have distinct habitat-associations that allow them to reduce interspecific competition through niche partitioning and would be best managed with a diverse set of successional stages.