FEATURE
Birds as agents of restoration
Worldwide , land degradation , which results from land-use change , has affected about 30 % of the total land area resulting in loss of biological diversity , changes in soil structure and health , and a decrease in ecosystem goods and services . According to future global scenarios , land-use change is expected to be the strongest driver of biodiversity loss by the year 2100 . The xeric regions of the Albany Thicket Biome ( ATB ) in the Eastern Cape Province of South Africa have experienced land-use change with the transformation of intact thicket into land for livestock grazing , resulting in dense intact thicket being broken up into a mosaic of bushclump and open habitat , changing the assemblage of species and the interactions between them such as fruit removal by birds .
Kelly Bernard
Current Address : Rhodes Restoration Research Group , Department of Environmental Science , Rhodes University E-mail : kellymonicatandi @ gmail . com
Once land has been degraded by landuse change it is possible to employ restoration initiatives to restore a healthy functioning ecosystem and bring back species that will help to promote the establishment of intact habitat . One way to do this in the ATB is to harness the natural functions of fruit-eating birds to promote the redistribution of thicket species in mosaic and degraded habitats . Fruit-eating birds play an important role in the distribution of the ATB by consuming and then dispersing fruit to viable microclimates allowing for seedling establishment and growth , promoting the maintenance or reestablishment of intact Albany Thicket .
A project conducted by a Rhodes University Honour ’ s student used artificial feeding trays to assess whether birds were more likely to feed on indigenous fruit of the small knobwood tree and crow-berry tree in bushclump habitat than in open habitat in the ATB . A second goal of the project was to assess whether artificial feeding trays would be a viable technique in the promotion of the redistribution of woody thicket species by birds in degraded areas of the ATB .
It was predicted that birds would remove more fruit in bushclump habitat
Figure 1 : A typical bushclump patch setup with three feeding trays set close together to assess the effect of fruit type on fruit removal by birds . The control tray is set to the side of the feeding trays and is covered with a 6.3 mm hardwire mesh to stop fruit removal by birds to account for the weight loss of fruit due to dehydration . Raisins were excluded from analyses as they were removed by Vervet Monkeys ( Chlorocebus pygerythrus ).
Figure 2 : A typical bushclump patch with an average height of 3 meters and a circumference of 36 meters .
where there was more protection from predators , more branches to perch on and more indigenous fruiting species than in open habitat . Artificial feeding trays were designed to allow only birds to feed and exclude feeding by small mammals and ants and were placed in both bushclump and open habitats .
09 Grassroots Vol 21 No 1 March 2021