Current claims of biodiversity crisis call for immediate conservation actions. These require the identification of priority sites for conservation based on an assessment of biodiversity patterns. Patterns of species richness are crucial in such endeavor. Also rarity, measured by the size of species’ geographical ranges, is often used as a single or complementary criterion. For instance, hotspots for conservation have been defined using either one or the other criterion. We apply a novel tool, range-diversity plots, which simultaneously analyze species richness and range size from a presence-absence matrix to identify sites and species with potential conservation value. We applied this tool to the Mexican avifauna and show how it can be readily used to conduct broad-scale conservation assessments. Mexican birds showed congruent patterns between richness and rarity, richer sites harbor small-ranged species. Also, we identified Mexican ecoregions harboring richness-rarity sites and compared our assessment with an exhaustive prioritization procedure. A range-diversity approach can be useful when fine-scale information is lacking, such as in poorly studied regions. We demonstrate that spatial congruence between richness and rarity can be easily identified and interpreted using range-diversity plots based solely on a presence-absence matrix, providing a transparent, robust and explicit application for conservation assessments. (C) 2012 Elsevier Ltd. All rights reserved.