Without these normal flora, the animal would not be healthy. The normal flora in a human's mouth contain many bacteria that are harmful and potentially disease causing to our pet birds. Food that is perishable such as fruits and vegetables are very likely to grow large numbers of disease causing bacteria if left in the cage at room temperature for long periods of time. Baby food formula mixed in the morning and refrigerated throughout the day and reheated and fed at night is a wonderful place for bacterial overgrowth to occur. Many of our baby birds are made sick with this practice.
Refrigeration slows bacterial growth.
Fresh foods from the grocery are bacteria laden since they have been handled by humans and possibly contaminated by other mammal wastes during storage and shipping. Mice and other vermin can carry bacteria to your food sources. Water sources are an enigma of their own. Pseudomonas bacteria is a potential threat to all of our birds on a constant basis. This bacteria loves to grow in your water faucet, particularly if your water lines are PVC pipe instead of copper.