Sinus infection can occur in any '''psittacine''' but is particularly common in imported grey parrots. It was largely thought to be associated with a diet deficient in '''Vitamin A''' however there is now some controversy surrounding its contribution to the disease<ref name="one">Lawton, M (1999) '''Management of respiratory disease in psittacine birds''' ''In Practice 1999 21: 76-8''</ref> <ref name="three">Stanford, M (2009) '''Respiratory Disease in Birds''' Royal Veterinary College Integrated Course ''RVC''</ref>. | Sinus infection can occur in any '''psittacine''' but is particularly common in imported grey parrots. It was largely thought to be associated with a diet deficient in '''Vitamin A''' however there is now some controversy surrounding its contribution to the disease<ref name="one">Lawton, M (1999) '''Management of respiratory disease in psittacine birds''' ''In Practice 1999 21: 76-8''</ref> <ref name="three">Stanford, M (2009) '''Respiratory Disease in Birds''' Royal Veterinary College Integrated Course ''RVC''</ref>. |