The utility of birds as bioindicators: case studies in equatorial Africa.

When site quality cannot be fully studied, due to lack of time or available specialists, the use of particular species as indicators has been proposed. However, species which indicate species-richness are needed for appreciation of biodiversity, whereas widespread stenotopic species are appropriate for habitat quality. Birds are potential bioindicators, uniting inherent biological and methodological advantages. Birds can only be bioindicators of habitat quality if they occur in the same habitat in all the sites under consideration. Standard bird counts and captures, and standard measurements of habitat-characteristics taken along chosen transects, yield avifaunal composition and relative density in pristine and man-changed areas in equatorial Africa, in two complex areas situated in the historical forest belt (Zaire and Cameroon). The use of these data for bioindication was examined. Segregation was found to be highest in undisturbed sites within the mosaic of present-day habitats. The present study proposes, for this particular region, the use of proportions in relative density of four common species among a particular family, the bulbuls, which all are well-characterized according to habitat. Nevertheless, the authors are fully aware that this indicator cannot be extended to other regions.