23 

 preference for areas of high solar radiation and/or a 

 preference for placing nests in line of the prevailing wind 

 for lofting from the nest (Smith and Murphy 1982, Ensign 

 1983, Marco Restani, pers. coram.) . Solar radiation may be 

 of importance in this high elevation population of 

 Ferruginous Hawks for when birds return from their wintering 

 grounds snow cover may still be present in the study area 

 and periods of inclement weather may occur in the spring 

 (pers. observ.) . This importance is borne out by the fact 

 that three of the seven nests with a generally northward 

 exposure (0-90° and 270-360°) were located in trees. 

 Ferruginous Hawks, by nesting in trees, may be able to 

 offset some of the harshness that they would experience when 

 ground nesting on a north-facing slope. 



I found the diet of Ferruginous Hawks in southwestern 

 Montana to be quite diverse. Hill's measures of diversity, 

 Nl and N2 , correspond to the number of abundant and the 

 number of very abundant species, respectively, in the diet 

 sample (Ludwig and Reynolds 1988) . Therefore, over seven 

 (Nl =7.5) different species were classified as abundant, 

 including ground squirrels, red-legged grasshoppers, Sage 

 Thrashers, northern pocket gophers, cottontail rabbits, 

 voles, and Horned Larks. Over four species were classified 

 as very abundant (N2 = 4.7). Much of the dietary diversity 

 may be attributed to the fact that Ferruginous Hawks in our 

 study area preyed heavily upon songbirds. Songbirds 

 accounted for nearly 2 0% of the diet, somewhat higher than 

 the 12.1% reported by Restani (1991) for the Centennial 

 Valley. Other researchers have noted that avian prey 



