Importance of the lilac-crowned parrot in pre-dispersal seed predation ofAstronium graveolensin a Mexican tropical dry forest

Abstract

Abstract:Parrots represent a large biomass of canopy granivores in tropical forests, and may be effective pre-dispersal seed predators. We evaluated the importance of the lilac-crowned parrot (Amazona finschi) as a pre-dispersal seed predator ofAstronium graveolens(Anacardiaceae) in tropical dry forest. Seeds were collected in fruit-traps beneath 22 trees to compare pre-dispersal seed predation by parrots and insects, and determine whether intensity of seed predation was related to fruit-crop size or the aggregation of fruiting conspecifics around focal trees. Ground-level exclosures were established to compare post-dispersal seed predation by vertebrates and insects. The lilac-crowned parrot predated 43% of seeds pre-dispersal, while insects predated only 1.3%. Intensity of pre-dispersal seed predation by parrots was significantly greater in high-fruiting 0.79-ha resource patches, and was not related to fruit abundance of the focal tree. Foraging parrots also discarded immature fruits below the tree, causing a total 56% pre-dispersal loss of seed production, which was greater than post-dispersal removal by vertebrates, mainly rodents (51%) or insects (36%). Our results show that parrots play an important role as pre-dispersal seed predators in tropical dry forests. The reduction of parrot populations in tropical forests may have consequences for seed predation, affecting recruitment patterns of canopy trees.