Avian responses to varying intensity of cattle production in Spartina densiflora saltmarshes of South-Eastern South America

Abstract

Saltmarshes of Spartina densiflora in south-eastern South America have been modified by anthropogenic activities, mainly production of livestock. We examined the effect of the intensity of cattle production on the structure of saltmarsh vegetation and the effect of these changes to vegetation on the richness, composition and size of the avian populations and the abundance of nests. The levels of cattle production were based on the combined intensity of prescribed burning and cattle grazing, classed as: (1) High grazing - High burning (HH), (2) Low grazing - Low burning (LL) and (3) No grazing - No burning (NN). Cattle production altered the vegetation structure of saltmarshes and indirectly modified the richness, composition and size of their avian populations and the abundance of nests. Saltmarshes with either LL or NN production levels were inhabited by tall grassland specialists and generalists and by species specialised to live in a mosaic of short and tall grassland patches. Conversely, saltmarshes with HH production levels were inhabited by short-grassland specialists. That avian species diversity does not differ between S. densiflora saltmarsh subject to low or no human impacts has several potential interpretations, which are discussed. These findings have implications for management of grasslands to maintain avian diversity. Journal compilation