Effects of habitat degradation on avian guilds in East African payrus Cyperus papyrus swamps

摘要

The density and species richness of bird communities in disturbed and undisturbed stands of papyrus Cyperus papyrus were compared. Point counts, corrected for different probabilities of detection in different swamps, suggested that the species richness of bird communities in stands of papyrus disturbed by burning, grazing or pollution was higher than in nearby stands that were not disturbed. However, there were fewer species and individuals of highly specialized birds or species characteristic of papyrus, in disturbed stands than in undisturbed swamps. At <1 ha~(-1)>, the density of Papyrus Gonolek Laniarius mufumbiri in Ugandan swamps was, for example, significantly lower in polluted and burnt sites than in undisturbed papyrus where up to 13 ha~(-1) were recorded in the centre of swamps. White-winged Swamp Warbler Bradypterus carpalis was only recorded in undisturbed papyrus. In the papyrus that fringes Lake Naivasha in Keyna, outside the geographical range of species restricted to papyrus, disturbance in the form of grazing selects against species classified as swamp-reliant. Species classified as generalist users of papyrus were much less sensitive to disturbance than specialists. The density of swamp specialists was also lower near the edge of swamps, where total species richness was higher. These results are discussed in relation to conservation management of papyrus swamps in East Africa.