Mean time and monetary cost per km−2 of surveyed area (viewshed) looking for suitable habitat for cliff-nesting vultures by using different methods.

Values were calculated from a sample of seven 10×10-km squares randomly located within the study area. The percentage of square surface prospected with each method is also shown (Viewshed). Time costs for Google Street View are mean values obtained from four different observers (see text for further explanations).