Fates of feathered fruit-eaters in fragmented forests
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Fruit-eating birds disperse many rainforest seeds, thereby influencing rainforest regeneration. The abundance of these birds may change following forest clearing, causing differences in seed dispersal between extensively-forested and fragmented areas. We assessed the responses of 26 frugivorous bird species to forest fragmentation by comparing their abundance among extensive tracts, remnants and regrowth patches of rainforest (16 replicate sites in each) in subtropical south-east Queensland, Australia. There were five species that were recorded in much lower numbers in remnants and/or regrowth than in extensive forest (“decreasers”), seven that showed higher abundance in remnants and/or regrowth than in extensive forest (“increasers”) and 14 whose abundance did not change substantially between the three habitat types (“tolerant” species). The decreasers included three fruit-specialist rainforest pigeons (the wompoo, rose-crowned and superb fruit-dovesPtilinopus magnificus, P. regina andP. superbus). The increasers were largely bird species with mixed diets, many of which also use non-rainforest habitats. Two decreasers and two tolerant species were substantially more abundant during summer than winter whereas two increaser and two tolerant bird species were more abundant during winter. No effects of altitude on seasonal abundance were apparent. The results of this study show that fragmented remnant and regrowth patches of rainforest do not adequately conserve the full set of frugivorous avifauna. Furthermore, lower abundance of negativelyimpacted birds in fragmented remnant and regrowth sites may lead to reduced regeneration of certain rainforest plant species due to a lack of seed dispersal in these habitats.