Bird nest predation in a southern Tunisian oasis habitat: No evidence of “edge effect”

Numerous ornithological studies conducted in patchy habitats have linked high intensity of nest predation with habitat edges. This “edge effect” hypothesis was primarily investigated in temperate, boreal and tropical fragmented forests, and there is a need for investigations from different habitat systems. Here we provide the results of one study on bird nest predation in relation to edge context in one oasis in southern Tunisia. Our aim was to assess the importance of nest predation as a source of nest failure in the studied oasis and to test if the edge effect hypothesis applies in this habitat system. We found that although predation represents an important source of nest failure in all studied species, the edge effect hypothesis does not seem to apply in the studied oasis. Indeed, daily nest predation rate did not vary with edge context for all studied species, which could be explained by the fact that nest predator guild is mainly composed of small species that use oasis interior and edges in similar ways. The effects of predators coming from the surrounding areas do not seem to significantly increase nest predation rates in oasis edges compared to oasis interior. We also found that nest predation rates were similar for all bird species, suggesting that among-species differences in nest concealment and nesting behaviour did not seem to account for nest survival in the studied oasis. However, further more detailed species-level studies are needed to test this hypothesis and to identify more accurately the determinants of nest predation in the oasis habitat.