Diets of Northern Goshawks (Accipiter gentilis) in western and eastern North America show regional differences. This variation may be explained by the opportunistic feeding behavior of Northern Goshawks and the greater number of potential prey species in western North America. We predicted that a population of Northern Goshawks in the Warner Mountains of California would take significantly more mammals than birds as prey. Goshawk diet in the Warner Mountains was determined by pellet analysis and prey remains. A total of 33 samples from 23 nest sites was collected and analyzed. Diets were quantified by determining the minimum number of individuals per sample at each nest site. As predicted, Warner Mountain Goshawks preyed more heavily on mammalian than avian prey species. Of the 221 individuals identified, 126 (57%) were mammals, while 95 (43%) were birds. These results are in accord with the suggestion that there are potentially more mammalian prey species in western North America than in eastern North America.
Promessi, Rebecca L.; Matson, John O.; and Flores, Mary
"Diets of nesting Northern Goshawks in the Warner Mountains, California,"
Western North American Naturalist: Vol. 64
, Article 10.
Available at: http://scholarsarchive.byu.edu/wnan/vol64/iss3/10