The habitat-heterogeneity hypothesis states that an increase in habitat heterogeneity leads to an increase in species diversity. Although community-level analyses of effects of habitat heterogeneity on species diversity are important, they do not reveal the mechanism through which heterogeneity affects diversity. In contrast, habitat associations of particular species suggest a potential mechanism whereby diversity is affected by habitat heterogeneity. The sand–shinnery-oak ecosystem of southwestern United States contains 2 habitat types: blowouts and matrix. Blowouts are small and infrequent wind-formed open patches without shrubs. These disturbances are surrounded by a dense shrub-dominated matrix, mostly containing the low stature oak, Quercus havardii. Habitat associations of particular species with respect to blowouts versus matrix were assessed using capture frequencies and species abundances. Only Dipodomys ordii was more abundant in blowouts than in surrounding matrix, and this only occurred during summer. This seasonal change could be a consequence of competition or predation. All other species showed a preference for the matrix. Considerations of scale and edge effects between blowouts and matrix may provide additional insight into habitat associations of rodents, leading to a deeper understanding of the mechanistic basis of diversity in this ecosystem.