Effects of habitat change and geographical variation on the bird communities of two Indonesian islands

Abstract

The effects of selective logging and other types of forest exploitation on bird communities are often studied latitudinally, i.e. a contemporaneous comparison of disturbed and pristine areas. Such an approach assumes that before disturbance those areas were equivalent. By comparing communities at a single site before and after disturbance, a so called longitudinal approach does not make that assumption but such studies can be resource intensive. In this study we adopt a latitudinal approach to explore the effects of disturbance on birds, but pay specific attention to whether natural geographically-based variation in the forest ecosystem may be a major contributory factor equal to, or greater than, effects of disturbance. Bird census data were collected from two Indonesian islands, Sumba and Buru. On Sumba the differences between habitat types in terms of species richness, species accumulation rates, and numbers of birds were swamped by simple site differences between the forest blocks sampled. On Buru, disturbed areas were more diverse than mature forest but it was still not possible to discount the effects of natural variation between forest areas. Although the islands support bird faunas which are rather similar in size and origin, local species diversities and abundances were significantly greater on Sumba. Substituting space for time is a common strategy in ecological research but the results of such studies should be viewed with caution.