Using an interactive map-based PDF, students learn key concepts related to biodiversity while developing data-analysis and critical-thinking skills. The Bird Island lesson provides students with experience in translating geospatial data into bar graphs, then interpreting these graphs to compare biodiversity across ecoregions on a fictional island. When the lesson is extended to include real data for Puerto Rico, students can explore distributions of selected bird species based on environmental attributes, making connections between each species' adaptations, habitat requirements, and distribution across the island. This introductory lesson provides a jumping-off point for field and Web-based biodiversity investigations.