My budgie has diarrhoea why?

He/she may have it because you are not feeding her/him Gravel rocks. the budgie needs it to slow down its digestive system. You can find this proudouct at any pet store. Ask for "Bird gravel" and the rest is up to the pet store assistant. sprinkle about 2 tbsp on the floor of the cage and a tsp on his food.

There is a good chance that you are feeding your budgie too much fruit, vegetables or plant matter. Budgies need a balanced diet, and if you feed them fruits and leafy green vegetables such as lettuce every day, this is too much, too often. Cut back on the sweet and leafy treats to perhaps once a week initially, and gradually progressing to every three days or so. One of the safest treats you can give regularly are grass seed heads from your garden (providing they haven't been sprayed with anything).