Three grassland bird species' responses to fire and habitat structure in southern Illinois, USA suggest broad benefits of grassland size and plant diversity

Grassland birds are the most rapidly declining bird guild in North America, largely due to extensive habitat loss and fragmentation. Because many grassland bird species have different habitat preferences, managing grasslands to provide habitat for a range of species can be a challenge. We used four years of data from southern Illinois, USA grasslands to estimate the influence of prescribed fire and habitat structure on nest survival, nest density, and abundance of three grassland bird species with different habitat preferences: Dickcissel (Spiza americana), Field Sparrow (Spizella pusilla), and Common Yellowthroat (Geothlypis trichas). We found that Dickcissels exhibited the strongest response to prescribed fire, as nest density and nest survival both increased after previously undisturbed grasslands were burned. Fire may have also benefitted Common Yellowthroats and Field Sparrows by reducing woody cover and increasing bare ground, both of which were characteristics associated with nest survival for these birds. Dickcissel abundance was positively related to plant diversity within a grassland and agriculture in the surrounding landscape (within 400 m of a grassland patch), and negatively related to edge-interior ratio. Field Sparrows demonstrated a positive association with woody cover and proximity to forests. Common Yellowthroats were associated with tall vegetation and agriculture in the surrounding landscape. Both Field Sparrows and Common Yellowthroats associated positively with habitat characteristics that reduced nest survival, suggesting potential adaptive mismatches. Our results suggest that periodic prescribed fire, increased plant diversity, and larger patch size may simultaneously benefit a broad variety of grassland bird species with different habitat preferences.