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Sour Crop - Candida, Thrush
Cause - This very common disease is caused by a fungus infection of the digestive tract. It is often associated with excessive use of antibiotics.
Symptoms - Infected birds become listless, won't eat, lose weight, develop a water-filled crop and vomit often. This vomit often has a very putrid odor. Sometimes, in lesser cases, thrush will show itself as just small whitish spots in the throat, which causes confusion with canker. Another much less noticed symptom, usually found only in adult birds, is feather pulling.
Prevention - Avoid overcrowding, maintain a sanitary loft, and most importantly, do not medicate indiscriminately.