Forest vegetation structure has more influence on predation risk of artificial ground nests than human activities

Abstract

As a major process affecting the reproductive success of birds, nest predation influences population density and dynamics and forces species to adapt to ecological and evolutionary time scales. The disentangling of potential natural and anthropogenic drivers of nest predation is crucial for the conservation of species. Thus, we investigated the effects of elevation, egg characteristics, vegetation structure and human activities on daily nest predation rates of artificial ground nests by baiting 700 artificial nests with quail eggs along an elevational gradient of about 1100m. After 25 days, we found an overall daily nest predation rate of 0.045. Our generalized linear mixed model revealed increasing daily predation rates with increasing forest management, no impact of recreational activities, and lower daily predation rates in the vicinity of buildings. Furthermore, daily predation rates declined with increasing density of near-ground vegetation and increased with increasing tree cover. Finally, we found no influence of elevation, matching of egg and ground colouration, and dead wood on daily nest predation rates. Our results revealed that the risk of nest predation depends more on vegetation structure than on current levels of recreational activities. Moreover, the negative relation of nest predation risk and near-ground vegetation indicates that the changing forest structure after natural disturbances (e.g. wind throw or bark beetle infestation), which is tolerated within the benign neglect strategy applied by the authorities of protected areas, decreases the predation risk, whereas salvage logging increases this risk.