Comparative impacts of fragmentation on birds in two bioregions in a biodiversity hotspot, the Cape Floristic Region

[摘要] Habitat loss and fragmentation are two of the most pressing threats to biodiversity. Avifaunaldiversity and integrity is under immense pressure from these two processes. We have mademajor advances in our understanding of avifaunal responses to habitat fragmentation, but mostlyfocus on either fragment scale and/or landscape scale influences of fragmentation on birds. Amore comprehensive approach to assessing the impacts of fragmentation was used in this study.The avifaunas of two different geographical regions and bioregions were surveyed and a multiscaleanalysis of avifaunal responses to fragmentation was attempted. The study sites include theWest Coast and East Coast Renosterveld Bioregions in the Cape Floristic Region, South Africa.Assemblage shifts, feeding guild compositional changes, species abundance variation and speciespersistence were examined at the three spatial scales. Time- and distance-restricted point countswere used to document birds that were directly dependent on the habitat fragments. Fortyfragments were selected in each bioregion and a once-off snapshot of the avifaunal richness anddiversity was obtained.Results indicate that the avifauna of the two bioregions responded differently to habitatfragmentation. In the East Coast Renosterveld Bioregion, the assemblages, guild compositionand species abundances were most accurately predicted by landscape configuration. Anassemblage shift occurred at 20 ha fragment area, compared to the 50 ha fragment area thresholdof the West Coast Renosterveld Bioregion's avifauna composition. In the West CoastRenosterveld Bioregion, fragment area was the better predictor of assemblage, guild compositionand species abundances. However in both bioregions, the persistence of common species wasequally sensitive to area and landscape scale effects.

[发布机构] Stellenbosch University