AN EXPERIMENTAL-STUDY OF THE IMPACT OF FERAL SWAMP BUFFALO, BUBALUS-BUBALIS, ON THE BREEDING HABITAT AND NESTING SUCCESS OF MAGPIE GEESE, ANSERANAS-SEMIPALMATA, IN KAKADU-NATIONAL-PARK

The impact of buffalo Bubalus bubalis grazing and trampling on magpie goose. Anseranas semipalmata breeding habitat and nest numbers was stu died over nine wet seasons (1980-88) at Kapalga within Kakadu National Park. Aerial photographs provided data to compare nest densities with in six vegetation types in an area where buffalo grazed throughout the study with an area where buffalo were removed midway through. Buffalo had no significant effect on the abundance or distribution of vegetat ion types important to geese for breeding. However, high densities of buffalo suppressed the growth of several other species, particularly t he grass Hymenachne acutigluma which increasingly displaced the deep w ater spike-rush Eleocharis sphacelata after buffalo were removed. The annual number of nests fluctuated between 7 and 2028, apparently in re sponse to rain. Most nests were built in the spike-rush/wildrice Eleoc haris spp./Oryza rufipogon association (71%) and in E. sphacelata (20% ). Buffalo trampling and grazing influenced the location of nests but not number. After buffalo were removed, more nests were built in deep water areas at the forest edge of the floodplain. Copyright (C) 1996 E lsevier Science Limited.