# There is no abstract for a Brevia article Endemism is a measure of geographic range restriction which is used to highlight regions with unique biota, found nowhere else on earth. Here, we develop a trait-based metric for a functional approach to endemism studies - functional endemism - and explore global patterns in birds. We find that the world’s islands and mountain ranges are hotspots of functional endemism in birds, highlighting the importance of these ecosystems for conservation.