24 

 usually contribute little to Ferruginous Hawk diet and that 

 a high proportion of avian prey in the diet may be inferred 

 to be the result of hawks preying upon non-preferred and, 

 hence, alternate prey during periods of low prey abundance 

 (Schmutz et al. 1980, Ensign 1983, Gilmer and Stewart 1983). 

 Without actual measures of prey abundance and diversity in 

 southwest Montana, it is difficult to postulate whether 

 avian species are alternate prey to this population of 

 Ferruginous Hawks. 



Vegetative diversity within 375 m 2 plots centered at 

 nests, as measured by Hill's Nl, was guite variable with 

 five of the six nests exhibiting values > 9.0 located in or 

 adjacent to the Centennial Valley. Additionally, seven of 

 the nine nests with Nl < 9.0 were further north in the 

 Beaverhead Valley. This trend may be due to different 

 precipitation regimes from the Centennial Valley northward 

 (and generally downward in elevation) and apparently was 

 analogous to the prey abundance gradient that I observed. 



CONCLUSIONS AND MANAGEMENT IMPLICATIONS 

 Ferruginous Hawks are successfully reproducing on the 

 public lands of southwestern Montana. Reproductive success 

 during 1992 was high and hawks chose a variety of substrates 

 upon which to nest. With the addition of the 15 previously 

 unknown active territories discovered during this study to 

 the 97 active territories described by Myers (1987), the 

 five or six active territories on the Blacktail Wildlife 

 Management Area (Dennis Flath, pers. comm.) and the 15 

 active sites in the Centennial Valley (Restani 1989) , I 



