Seed dispersal by large, mobile vertebrates plays a key role in shaping plant spatial dynamics and community structure. However, how variation in animal population size influences the magnitude and spatial scale of seed-dispersal remains poorly understood. We used and agent based modeling approach to simulate stomatochoric seed dispersal by the endangered Lear’s Macaw (Anodorhynchus leari) to evaluate how changes in population size affect the seed-dispersal function it provides for the licuri palm (Syagrus coronata), a keystone species in the Caatinga dry forests of Brazil. By simulating macaw movements under different population scenarios, we show that both the frequency and distance of seed dispersal events increase disproportionately with population size. Small populations result in highly localized seed deposition, whereas larger populations promote a considerable expansion in the frequency and length of long-distance dispersal (LDD). These findings suggest that the ongoing recovery and reintroduction of A. leari may not only benefit the macaws themselves but also enhance the regeneration and connectivity of S. coronata populations. More broadly, our results emphasize the potential for population recovery of large frugivores to restore lost ecological functions and reveal stomatochory by parrots as an overlooked but functionally significant dispersal mechanism for large-seeded plants.