Rat eradication and the resistance and resilience of passerine bird assemblages in the Falkland Islands

1. Norway rats (Rattus norvegicus) were introduced to the Falkland Islands and are detrimen-tal to native passerines. Rat eradication programmes are being used to help protect the avi-fauna. 2. This study assesses the effectiveness of eradication programmes while using this conserva-tion practice as a natural experiment to explore the ecological resistance, resilience and homeostasis of bird communities. 3. We conducted bird surveys on 230 islands: 85 in the presence of rats, 108 that were histori-cally free of rats and 37 from which rats had been eradicated. Bird detection data were used to build occupancy models for each species and estimate species–area relationships. Count data were used to estimate relative abundance and community structure. 4. Islands with invasive rats had reduced species richness of passerines and a different com-munity structure than islands on which rats were historically absent. Although the species richness of native passerines was remarkably similar on eradicated and historically rat-free islands, community structure on eradicated islands was more similar to that of rat-infested islands than to historically rat-free islands