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 p opulation declines, partly because of landuse practices associated wit h agricultural activity. The aim of this study was to compare the habi tat correlates of songbirds breeding in native mixed-grass prairie wit h patterns found in introduced vegetation dominated by crested wheat g rass (Agropyran 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, Can ada. In addition to having higher plant species richness and diversity , native vegetation consisted of significantly more grass and sedge co ver, less bare ground, deeper litter, and higher density within 10 cm of the ground than introduced vegetation. Bird species richness and di versity 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, re gardless of vegetation type. Sprague's Pipits (Anthus spragueii) showe d a curvilinear increase along the same gradient, occurring in high nu mbers where habitats offered an intermediate level of cover. Our findi ngs suggest that species richness and diversity within songbird commun ities and the abundance of some species may be reduced where conversio n to crested wheat grass results in more open habitat.