Waterbird herbivory on a newly created wetland complex: potential implications for site management and habitat creation

Estimations of waterbird herbivory at a newly created wetland, indicate that overwintering waterbirds have the potential to remove a large proportion of the above-ground macrophyte standing crop in the main lagoons. Observed lake state switching and changes in macrophyte species composition may have been linked, in part, to waterbird herbivory. Significant differences were observed in the distribution of certain species of waterbird between the lagoons, which may reflect food preferences. Between 30% and 50% of the herbivorous waterbird community utilised alternative on-site feeding areas over the winter period thus reducing the impact of grazing intensity in the larger open water areas. These results emphasise the advantages of incorporation of site heterogeneity, specifically distinct hydrological units, within the design of wetland creation schemes. Hypereutrophic conditions, with turbid water and dense filamentous algal blooms were experienced on the Reservoir Lagoon yet the lagoon supported high densities of overwintering birds (> 100 individuals ha^–1. This led to an alleviation of grazing pressure on other water bodies thereby promoting the development of macrophyte communities elsewhere on site. The need for work to provide a better understanding of critical thresholds of herbivory in determining community composition and abundance, and particularly the role of eutrophication in these processes is highlighted.