A multi-year study conducted on San Joaquin Experimental Range in California, seemingly still the largest food study to date done for red-tailed hawks with 4031 items examined, showed that throughout the seasons the 722 grams California ground squirrel (Otospermophilus beecheyi) was the most significant prey, accounting for 60.8% of the breeding season diet and about 27.2% of the diet for hawks year-around.