Appendix C (FIG. C1). Continuous Boyce curve (c.f. Hirzel et al. 2006), calculated from the independently collected black grouse data. The ratio between the number of evaluation points predicted by the model (P) and the number of points expected in case of a uniform random distribution (E) is plotted against each probability value (p) between 0 and 1. Only wintering areas were considered, for which the predicted probability of black grouse presence was larger than expected by chance (i.e. for which P/E > 1).
Hirzel, A. H., G. Le Lay, V. Helfer, C. Randin, and A. Guisan. 2006. Evaluating the ability of habitat suitability models to predict species presences. Ecological Modelling 199:142–152.