Identifying the factors that influence the extinction risk of animals is essential in conservation biology because they help identify endangered species and provide the basis for their preservation.We present a comparative study that uses data from the literature on the diet and morphological specialization of European and North American bat species to investigate the effect of specialization on extinction risk. We focused on bats because many species are endangered and their high ecological diversity makes them a good model system for our purpose. After correcting for phylogenetic inertia, we compared the influence of dietary niche breadth as a measure of food specialization and of wing morphology as a measure of foraging strategy, habitat adaptation, and migratory ability on the vulnerability of 35 insectivorous bat species. Our results do not support the hypothesis that a narrow dietary niche breadth is related to high extinction risk. Instead they suggest that habitat specialization, which is reflected in wing morphology, influences the extinction risk of bats. Our study shows that an initial risk assessment in temperate-zone bats could be based on data of wing morphology but not on dietary data obtained from fecal analyses.