1. Handbook of the birds of the world volume 2: new world vultures to Guineafowl;del Hoyo,1994
2. Handbook of the birds of the world volume 5: Barn-owls to hummingbirds;del Hoyo,1999
3. Understanding the bird of prey;Fox,1995
4. Care, captive breeding and conservation;Parry-Jones,1988
5. Birds of prey, health & disease;Cooper,2002