Competing for seed dispersal: evidence for the role of avian seed hoarders in mediating apparent predation among oaks

In communities of large-seeded tree species, generalist seed hoarders often link the temporally variable dynamics of various species in ways that can result in indirect ecological interactions. A special case of such interactions is ‘apparent predation’ – when variation in seed production of one tree species changes the outcome of the interaction between seed hoarders and another tree species from seed dispersal mutualism to predation. We investigated how two species of avian hoarders responded to differences in acorn availability among individual valley oaks (Quercus lobata) and across a landscape dominated by blue oaks (Q. douglasii) to determine whether seed dispersal and predation dynamics result in apparent predation between these oak species. California scrub-jays (Aphelocoma californica), high-quality seed dispersers with large spatial scales of resource perception, showed strong numerical and functional responses to individually large Q. lobata acorn crops when landscape-level...