Avifaunal and habitat changes resulting from conversion of native prairie to crested wheat grass: patterns at songbird community and species levels

Many North American grassland songbirds are experiencing significant population declines, partly because of land-use practices associated with agricultural activity. The aim of this study was to compare the habitat correlates of songbirds breeding in native mixed-grass prairie with patterns found in introduced vegetation dominated by crested wheat grass (Agropyron pectiniforme). We assessed plant species composition, habitat structure, and bird species diversity over 2 years to document species- and community-level trends in southwestern Saskatchewan, Canada. In addition to having higher plant species richness and diversity, native vegetation consisted of significantly more grass and sedge cover, less bare ground, deeper litter, and higher density within 10 cm of the ground than introduced vegetation. Bird species richness and diversity and the abundance of Baird's Sparrows (Ammodramus bairdii) and Savannah Sparrows (Passerculus sandwichensis) increased significantly along a multivariate gradient from open to more sheltered habitat, regardless of vegetation type. Sprague's Pipits (Anthus spragueii) showed a curvilinear increase along the same gradient, occurring in high numbers where habitats offered an intermediate level of cover. Our findings suggest that species richness and diversity within songbird communities and the abundance of some species may be reduced where conversion to crested wheat grass results in more open habitat.