Thi s p ower fu l bi rd reli es p rim ar ily on lemm ings a nd other rodents for food, b ut at ti mes when these pr ey a re not av a ilab le, or during the p ta rmi gan nesting peri od, they m ay switc h to ptar miga n young. As op por tuni stic hunter s, they feed on a wide v ar i ety of s ma ll m a mma ls a nd bi rds.