An aerial sightability model for estimating ferruginous hawk population size

It has been possible to develop an aerial sightability model to estimate ferruginous hawk population size in two study areas in Wyoming. It was established that presence or absence of ferruginous hawks at the nest site did not seem to affect nest-detection rates. For active nests, the detection rate was 41.4%, while for inactive, natural nests the detection rate was 41.5%. Nest status was not an important predictor in the multiple regression model. Sightability modelling needs detailed planning and data collection, but has considerable advantages over single and stratified correction factors, double-count estimators and line transect.