Nest predation in Patagonian wetlands: predator assemblage and microhabitat characteristics

Multiple factors influence predation risk, ranging from habitat conditions to the composition and behaviour of predators. Although these factors are well documented for forest ecosystems, there is little evidence for wetlands, especially within Patagonia. Using artificial nests and camera traps, we documented the nest predation rates and predator assemblage of birds nesting in wetlands of the Patagonian steppe. We also determined the effect of vegetation cover on nest survival and studied the variation in predator groups according to nest placement: nests located in an open wetland, peripheral grassland to the wetland, and nests located in shrubs at different heights. We found 84% of nests failed, counting birds, mice, and armadillos as the main predators. Vegetation cover affected predation events of birds and small mammals, but not those of larger mammals. In turn, small mammals preyed on nests exclusively located in peripheral grassland, medium mammals preferred nests placed in open wetlands, and predation by birds was irrespective of open wetlands and grassland. We also found differences in nest predator assemblage between nests placed on the ground and in shrubs, with birds being the main predators of nests located above ground. These results can be attributed to differential habitat use and movement patterns specific to each predator group. Therefore, the identity, density, and behaviour of predators should be taken into account when planning conservation strategies for birds breeding in wetlands.