Drivers of Bird and Rodent Assemblage Composition in Rangelands of Southern Mexican Plateau

Rangelands provide ecosystem services for livestock and habitat for many wildlife species. However, the key features that determine their value for biodiversity conservation need to be assessed regionally. To elucidate the structural attributes that drive bird and rodent assemblages in semiarid rangelands in the southern Mexican Plateau, we studied patches of rangelands dominated by herbaceous plants (open) and xerophytic shrub communities (closed). We hypothesized that different guilds and species of birds and rodents are influenced differently by rangeland condition and different habitat components, and that bird assemblages had a higher turnover rate between patches than rodents. We surveyed the birds and rodents during the three regional climatic seasons and measured ground plant cover of herbs, shrubs, nopales, and trees. Through an information-theoretic approach we tested the effect of range condition and season on all variables of habitat and bird and rodent species richness and abundance. Habitat components (shrubs and nopales) most often included in the best/most parsimonious models explained bird and rodent abundances. Rodent species turnover is lower among rangeland plots of the same type geographically separated than between nearby plots of different type. In contrast, bird species turnover was higher because their higher mobility allows them to explore landscape patches than might offer complementation and/or supplementation. Rangelands in the southern Mexican Plateau should be viewed not only as livestock-producing areas but also as landscape components that can and should be used to effectively support biodiversity conservation, complementing the conservation role of other regional habitats. The high biodiversity conservation potential of the rangelands we studied should be recognized, and both habitat conditions should be incorporated in any regional conservation plans