The crop of an adult bird can be filled with thick mucus and crop impactions can occur. In adults, beak abnormalities and dead patches on the tongue can be caused by this fungi. Yeast can also be found in the lower digestive tract. This will often reveal such infections. Yeast can also occasionally cause respiratory infections.
Birds treated with antibiotics can develop a secondary respiratory infection caused by yeast.
Yeast are found everywhere in the environment. It can develop on spoiled food. For this reason, fresh fruits, vegetables and table food should never be left for more than a couple of hours in the bird's cage. In the summer, food can spoil in less than an hour. Poor hygiene can also spread yeast infections.