SEED DISPERSAL BY MANAKINS (AVES: PIPRIDAE) IN A SPECIES-RICH TROPICAL WET FOREST

LOISELLE BA; BLAKE JG; BLENDINGER PG

Brisbane, Australia

Simposio; FOURTH INTERNATIONAL SYMPOSIUM / WORKSHOP ON FRUGIVORES AND SEED DISPERSAL; 2005

Fleshy-fruited plants dominate the understory of Neotropical wet forest, and birds are their principal seed dispersal agents. Neotropical plant and bird species richness arguably reach their greatest local diversities in western Amazonia, where 1,104 species of trees (greater than 10cm dbh) have been recorded in a 50 hectare tree plot, and over 525 species of breeding birds have been recorded within a 650 hectare biological station. Forests of western Amazonia are approximately three to four times more species-rich than well-studied wet forest sites in Meso-America. From the perspective of frugivory and seed dispersal processes, one might predict that ecological roles of fruit-eating animals overlap more broadly (i.e. are more substitutable) in the species-rich forests of western Amazonia when compared to wet forest sites in Meso-America. Here we investigate this hypothesis by comparing overlap in fruit and habitat use by manakins (Aves: Pipridae) in wet forests of eastern Ecuador and Costa Rica. In the former site, six species of ‘true’ manakins regularly co-occur in upland terra-firme habitats, whereas in the latter site, two species, one of which is an altitudinal migrant, co-occur in undisturbed upland forest. Support of the hypothesis that diversity affects ecological overlap in seed dispersal function would suggest that species-rich forests in western Amazonia may be more resilient to population variation or even local extinction of frugivores than are forests in Costa Rica.