Ravens exploit wildlife roadkill and agricultural landscapes but do not affect songbird assemblages

Abstract

Future land-use change could supplement populations of opportunistic predatory birds, such as corvids, resulting in amplified predation pressure and negative effects on populations of other avian species. We investigated whether Forest Ravens (Corvus tasmanicus) were more likely to be observed in modified landscapes and in areas of higher roadkill density in south-eastern Tasmania. Following this, we examined the effect of Forest Raven density on the abundance of other birds. We surveyed birds along roadsides to investigate the effects of land-use and raven population density on the presence of smaller birds/songbirds. We used species distribution models and generalised linear models to assess the habitat and population dynamics of Forest Ravens. Roadkill presence increased the probability of observing ravens more than six-fold. Forest Raven presence was also higher in agricultural areas than in forested and urban areas. There was no effect of Forest Raven abundance on species richness or abundance of smaller songbirds. This null result may be due to seasonal effects or because ravens moderate the presence or abundance of other avian predators. However, the interactions of meso-predators with other species are complex, and further work is required to assess the long-term effects of anthropogenic supplementation of ravens on the ecosystem. Show more