During your bird's complete physical exam, the doctor will take a stool sample and run a Gram's Stain. By looking at the sample under the microscope, your veterinarian can tell a lot about your bird. The gastrointestinal system, where the feces accumulates before it is eliminated, is a miniature environment of its own. The balance of "good" bacteria with other inhabitants of the gastrointestinal system respond to changes in the diet. Your veterinarian may also see early indications of potential disease in the feces before you can even tell the bird is sick.