Movements of organisms between habitat remnants can affect metapopulation structure, community assembly dynamics, gene flow and conservation strategy. In the tropical landscapes that support the majority of global biodiversity and where forest fragmentation is accelerating, there is particular urgency to understand how dispersal across habitats mediates the demography, distribution and differentiation of organisms. By employing unique dispersal challenge experiments coupled with exhaustive inventories of birds in a Panamanian lacustrine archipelago, we show that the ability to fly even short distances (< 100 m) between habitat fragments varies dramatically and consistently among species of forest birds, and that this variation correlates strongly with species' extinction histories and current distributions across the archipelago. This extreme variation in flight capability indicates that species' persistence in isolated forest remnants will be differentially mediated by their respective dispersal abilities, and that corridors connecting such fragments will be essential for the maintenance of avian diversity in fragmented tropical landscapes.