The Variable Hawk, or Geranoaetus polyosoma, is a common if confusing bird of prey in open habitats in western and southern South America. The confusing part? Its taxony is disputed, with some splitting it, as wikipedia points out, “Into the widespread red-backed hawk (G. polyosoma) and the Puna hawk or Gurney’s hawk (G. poecilochrous) of the central and north Andean highlands, but the differences between the two are unclear.”
Length can range from 45 to 62 cm (18–25 in) and wingspan ranging from 113 to 151 cm (45–60 in). Weight can range from 800 to at least 1,800 grams (1.8-4 lbs). The Puna hawk subspecies generally considered to be at the larger end of the size spectrum and the red-backed hawk at the smaller (Juan Hernandez hawk being intermediate), but these distinctions are difficult at best in the field. Overall, however, this species rates as a large Buteo.