1. Anon 1954 Note on Spotted Eagle Owls. Dept. of Nature Conservation Report 11: 28. Union of South Africa Provincial Administration of Cape of Good Hope
2. Armstrong , E. A. 1947 Bird display and behaviour. London.
3. The nature and function of displacement activities;Armstrong;Symposia Soc. Exper. Biol.,1950
4. A report on the birds of north-western Alaska and regions adjacent to Bering Strait;Bailey;Condor,1926
5. Bailey , A. M. 1948 Birds of Arctic Alaska. Colorado Mus. Nat. Hist., Pop. Ser. 8