Fruit removal by large avian frugivores varies in relation to habitat quality in continuous neotropical rainforest

Abstract

Animal-mediated seed dispersal shapes key ecological processes including seedling recruitment and demography. Anthropogenic activities have substantively impacted tropical habitats, yet the degree of sensitivity exhibited by different frugivores to changes in habitat quality and how this may impact seed dispersal outcomes remains poorly understood. This is particularly true in contexts of low to moderate habitat alteration. To address this knowledge gap, we characterized the diurnal disperser community for an ecologically important canopy palm, Oenocarpus bataua, in continuous forest with differing degrees of human modification in northwest Ecuador. Our specific goal was to assess the degree to which visitation and fruit removal rates vary in relation to fine-scale forest structure. Frugivory and seed dispersal (i.e., removal of fruits with intact seeds) was dominated by three large bird species; smaller birds and some mammals visited fruiting trees but did not substantively contribute to seed dispersal. One of the three effective dispersal agents, the Long-wattled Umbrellabird (Cephalopterus penduliger), an endangered species threatened by habitat loss and degradation, exhibited higher visitation and fruit consumption rates in areas characterized by denser canopies, suggesting preference for foraging in undisturbed habitat. In contrast, two relatively common toucan species, Chocó Toucan (Ramphastos brevis) and Chestnut-mandibled Toucan (R. Swainsonii), exhibited no variation in foraging behavior in relation to the habitat metrics we assessed. These findings highlight the degree to which differences in sensitivity to habitat disturbance among frugivore species may impact foraging ecology and suggest that variation in forest structure within continuous forest can impact seed removal and seed dispersal processes.