Parrot owners have one big advantage over the owners of other pets -- when a healthy parrot poops in the house, there is no smell. If a smell exists, it's time to get your parrot to the vet.
Why No Smell
Parrot droppings do not smell, due largely to the parrot's diet. Parrots eat fruits, veggies, nuts and seeds, which generally produce less odor in waste. Parrots do not eat meat, which, due to sulfides in animal tissue, often generates foul-smelling waste in mammals. Also, parrots do not have the anal scent glands that mammals have, nor a cecum, which is a sac on mammals' large intestines that ferments foods and produces gas.
Because their droppings are essentially odorless, a foul odor in fresh droppings is an easily noticed indicator that your bird may be sick. If he did not eat anything unusual to produce the smell, such as broccoli, which is high in sulfur, your bird could be suffering from an infection in the digestive tract. It will most likely be a bacterial or yeast infection. Most birds hold their poop overnight until morning, so it is best to check then for signs of illness.
Steatorrhoea is a condition whereby excess fat is produced in excrement. It often is the result of a bacterial infection in birds and may cause bulky feces with a foul odor. Several types of bacteria affect birds, the most common being E.coli, citrobacter, strep and staph. According to AvianWeb, these bacteria are usually associated with water, sand, grit, seed, old food, humid areas, dusty spots and wet cages. They can affect the kidneys and liver.
Giardia is a parasite in drinking water that festers in the intestinal tract and is passed through feces. While the symptoms of an infection are often little more than irritating for parrots, giardia parasites can produce diarrhea with pungent odor. Chronic or recurring diarrhea with a smell is a likely indicator of an infection. As with any instance of smelly droppings, get your parrot to the vet immediately.