An appraisal of bird-mediated ecological functions in a changing world

Abstract

Birds perform several ecological roles for ecosystem functioning and generate great benefits for human population in some circumstances. However, environmental disturbances, mostly due to anthropogenic actions, have caused a decrease of bird diversity and can lead to the loss of their functions in the remaining habitats. Here, we conducted a scientific literature review to understand the general trends on the ecosystem functions executed by birds and the possible effects of environmental disturbances on them. Our research was conducted in September 2016 in Google Scholar, Scopus, and Web of Science databases, which returned 154 papers that targeted the importance of birds to the ecosystems’ maintenance. Among the studies (n=99) that effectively assessed the ecological role of bird species, most were conducted in natural habitats (n=63), and the most evaluated function was invertebrate population control (n=70). About 58% of the publications related some environmental characteristic to the ecological function, but patch and landscape-scaled factors were poorly investigated. Furthermore, 52% of the papers showed that the ecological function of birds can arise from a cascade effect on other trophic levels, though this may depend on the environmental characteristics. Despite the numerous studies in the ornithology field, the ecological roles of birds in several ecosystems are still poorly understood. Future research should consider others ecological functions mediated by birds, such as disease control, and must take different spatial scales and human modification of habitats into consideration, enabling generalizations based on ecosystem type and landscape composition variation.