Nest predation management: Effects on reproductive success in endangered shorebirds

Many species have suffered population declines through loss of suitable habitat. In addition, current agricultural land use and human settlements favor generalist predators, which pose an increasing threat to ground-nesting bird species such as shorebirds (waders). During the last 2 decades, nest exclosures have been used to control nest-predation rates and often improved hatching success. We evaluated the effectiveness of protective nest-cages to boost reproductive success in the endangered southern dunlin (Calidris alpina schinzii) and ultimately to halt the population decline. We found that exclosures successfully increased the survival probability of nests and, thereby, the number of hatchlings, without markedly elevating the predation rate on incubating adults. Nest exclosures did not, however, translate into an increased number of fledglings and recruits produced/breeding adult in the population, showing that factors other than nest survival are also important for population development. Our results highlight that conservation efforts aimed only at removing high nest-predation pressure may be insufficient to preserve declining species such as the southern dunlin.