Research was conducted to determine the effect of prey numbers on the nesting success of the Ferruginous Hawk (Buteo regalis). Conditions associated with nest site selection were also established. Frequent visits were made to active nests to determine clutch sizes, hatching dates and fledging success. Prey remains were collected from nests and analyzed. Kilometer square transects were made throughout the study area in 1974 to determine jackrabbit densities. A drastic decline in numbers of Ferruginous Hawks occurred. The number of young fledged also declined throughout the study while nestling mortality increased. Jackrabbit numbers were high in 1972 and then declined prior to the spring of 1973. The decline in hawk numbers appeared to be directly correlated with the reduction in prey densities. No directional trend was evident in nest exposure. Shade was not an apparent requirement in nest site selection. Tree nests tended to be in isolated trees that were taller than those surrounding them.