TROPICAL COUNTRYSIDE BIRD ASSEMBLAGES: RICHNESS, COMPOSITION, AND FORAGING DIFFER BY LANDSCAPE CONTEXT

Abstract

In tropical regions worldwide, large tracts of native rain forest have been replaced by agricultural systems. Appropriate management of these systems may contribute to biodiversity conservation, but we have limited knowledge of the effect of different management strategies on species persistence. We examined the capacity of tropical coun- tryside in southern Costa Rica to provide resources for avian frugivores. Bird assemblages visiting fruiting Miconia trees were recorded in five landscape contexts: sites near (<2 km from) a large (227-ha) rain forest remnant, split between high and low agricultural intensity; sites far (5-8 km) from the remnant, similarly split; and the remnant itself. Across all landscape contexts, 73 native bird species were observed taking fruit from Miconia. The composition of frugivore assemblages differed significantly among agricultural landscape contexts. Species richness was highest in near, low-intensity sites (21.5 ? 1.79, mean ? 1 SE) and lowest in far, high-intensity sites (14.1 ? 0.89). The visitation rates of frugivores did not differ among landscape contexts for all species combined, but there were significant differences in the frequency of visits for 10 individual species. Large, socially dominant frugivores were common visitors to trees in far, high-intensity agricultural sites, whereas the visitation rates of many smaller, subordinate frugivores (e.g., small tanagers) declined with distance from the large rain forest remnant or in high-intensity sites. Also, some forest- dependent species (e.g., White-ruffed Manakin, Corapipo altera) were infrequently re- corded at fruiting trees in high-intensity and far sites. However, trees in far sites provided resources to species that use both forest and agricultural habitats. Isolated fruiting trees in our study area appear to be an important resource for many avian frugivores. Use of these trees by a wide range of species is enhanced by their proximity to relatively large areas of native rain forest. Low-intensity agriculture that incorporates fruiting trees as part of live fences, windbreaks, or shade and allows for the preservation of rain forest remnants, would be beneficial to biodiversity conservation in the tropics and may facilitate the regeneration of bird-dispersed rain forest plants.