Core_dataset.csv

The island of New Guinea is home to the third largest continuous rainforest in the world, which is increasingly threatened by large-scale deforestation and forest conversion. Despite this, there is little scientific data on the highly biodiverse local avifauna, and in particular on its response to anthropogenic disturbances. Our study attempts to address this problem by examining bird communities in human-altered rainforests in lowland Papua New Guinea. Using point counts, we surveyed birds in a primary forest control site (P1), in primary forest fragments isolated by logging (P2), in secondary forests that have regrown after small-scale agriculture (S1), and in secondary forests that have regrown after clear-cutting (S2). We used generalized linear mixed-effect models to analyse bird species richness, density (abundance per hectare) and community structure. Total bird species richness was similar in P1 and S1 forests, but decreased significantly in P2 and S2 forest. Contrasting patterns in community metrics were observed for different bird feeding guilds. For example, we detected increasingly severe decreases in insectivore species richness in S1, P2, and S2 forest. In the S2 forest, there was also a collapse in the density of insectivore assemblages. Frugivore species richness decreased strongly in the P2 and S2 forest, but this was not accompanied by changes in assemblage density. Nectarivores showed a positive response to forest change by gradually increasing their assemblage density in human-modified forests, though there was no change in their species richness. Our results indicate that lack of connectivity with contiguous primary forest is a key element in avian biodiversity loss, which is further amplified by changes in forest structure. As logging concessions take up an increasing proportion of Papua New Guinea´s landscape, successful conservation will only be possible if large intact forest reserves are maintained.