Medium sized falcon. Length is 16-20" (from the head to the tip of the tail) with a wingspan of 37 to 43 inches (tip to tip.) Females average 15-20% larger than males. Individual weight can range from 16 ounces (small male) to 53 ounces (large female.) All birds have a distinctive malar stripe and uniformly patterned underwings. Immature birds are brown with heavy vertical streaking on breast/abdomen. Adults are a bluish/black with light barring on belly.