NEST SUCCESS AND PRODUCTIVITY OF FERRUGINOUS-HAWKS IN NORTHERN MONTANA

In 1993 - 1994, we investigated nest success and productivity of Ferru ginous Hawks (Buteo regalis) in northcentral Montana. The 171-km(2) st udy area contained a variety of habitats, a high density of breeding r aptors, and 24 occupied Ferruginous Hawk territories. Only 42% of occu pied nests produced fledglings. Occupied territories produced an avera ge of 0.96 fledglings (SE = 0.19). Successful nests produced an averag e of 2.30 fledglings (SE = 0.21, n = 20). Lagomorphs were scarce on th e area. Richardson's ground squirrels (Spemrophilus richardsonii) were more numerous along the edges of cropfields and roads than in grassla nds. Multiple regression indicated that Ferruginous Hawk nests closer to cropfields and roads and farther from other breeding raptors produc ed more young than other nests. Thus, habitats altered by humans, whic h were not extensive (20% cultivated), apparently had higher densities of ground squirrels and thereby benefited breeding hawks. However, be cause our multivariate analysis was exploratory and based on a moderat e sample size, our results should be interpreted cautiously and furthe r evaluated in future studies.