After this he was transferred to the Birds of Prey Foundation in Boulder, Colorado, where he spent almost a year in the large flight cages to practice flying. He never regained full strenth and so was returned to us to be trained. He will fly around his cage now, but due to calcification of the joint he can't sustain flight enough to be released. They prey mainly on small mammals, some birds, amphibians and reptiles. Like kestrels and unlike most other raptor, the sexes can be differentiated by their color.
Males are grey with black wing tips, and females are a rusty brown color.
They have owl-like facial discs, which helps them locate prey by hearing while flying low over the ground at dawn or dusk. Both sexes have a white patch on their rump, by the base of their tail. They nest on the ground, raising 4-6 young. Our male harrier was found near Pueblo, Colorado, with a fractured right humerus in September 1989. His wing needed to be amputated at the shoulder due to severe bone necrosis.