Northern goshawk diets in ponderosa pine forests in northern Arizona

Abstract

Little dietary information exists for northern goshawks (Accipiter gentilis) in the southwestern United States. I conducted 1,539 hours of direct observation at 20 active goshawk nests in ponderosa pine forests on the North Kaibab Ranger District, Arizona, 1990-1992. I recorded 385 prey deliveries at a mean delivery rate of 0.25/hr. I identified 63 deliveries to class, and 307 to genus or species. Golden-mantled ground squirrels (Spermophilus lateralis) and cottontail rabbits (Sylvilagus spp.) were the most common mammalian prey species (41%). Stellar's jays (Cyanocitta stelleri) and northern flickers (Colaptes auratus) were the most common avian prey species (16%). Mammals and birds accounted for 76 and 24% of the prey observed, and mammals accounted for 94% of the biomass used by northern goshawks. I compared the characterization of diet of northern goshawks based on direct observation to the characterization of diet based on prey remains. Diet based on prey remains differed from diet based on direct observation for individual prey species and the proportion of mammals and birds. Goshawk diet information based on prey remains should be interpreted cautiously. (Abstract shortened by UMI.)