Effect of the Weed Chrysanthemoides monilifera (Bitou Bush) on Bird Communities

Abstract

Bird communities in native coastal woodland were compared with those in woodland infested with Chrysanthemoides monilifera rotundata (bitou bush) in order to determine the impact of infestations of this weed on birds. Little evidence was found to suggest that bitou bush negatively affected the bird communities as a whole. Overall, the total number of birds in each type of habitat did not differ while numbers of species differed only at one area.

Weed infestations have a differential impact on foraging groups. Canopy-feeding generalists and understorey insectivores showed differences in abundance and species richness in a few areas, with greater numbers in weed sites than in native sites. Temporal variation in weed-site use was also evident for canopy foragers. For these groups, weed infestations are providing at least some resources, although the details of resource use need to be investigated further.

Species richness and abundance of birds relying almost exclusively on plant material were negatively affected by weed infestations, indicating that this foraging guild may not be provided with adequate resources in weed-infested habitats. Similarly, although numbers were low, scavengers and raptors also showed lower abundances and species richness in weed-infested habitats. For these foraging groups, management programmes to rehabilitate weed-infested habitats are likely to have a positive effect on numbers.