Designing lowland landscapes for farmland birds: scenario testing with GIS

Habitat association models have recently been constructed for two farmland bird species: the skylark (Alauda arvensis) and the yellowhammer (Emberiza citrinella). These models are based on a number of predictor variables which describe habitat variation measured at several farms in Oxfordshire, UK. They explain a high proportion of the variation in territory density and species occurrence for these two species and have been incorporated within a GIS. This system allows the user to manipulate the landscape, both structurally (by altering and/or removing boundaries) and agronomically (by changing the nature and timing of the cropping). The bird models are then reapplied to this changed landscape and the potential impact on the two species can be visualised in the form of a map. By comparing this to the baseline situation the degree and direction of change can be seen. As long as the assumptions and limitations of the underlying models are clearly understood, the GIS visualisation allows the ecological knowledge encapsulated in the models to be presented in a powerful and intuitive manner. The result is a system, which can be used for advisory work and policy advocacy for farmland birds.