Water must be changed every day and even twice a day in the summer. Water in the feeders and bottles goes stale very quickly and if drank by the bird, can cause illness.  If the bird has a tendency to drop food in the water container or to bathe in it, it must also be changed. Acrylic bottles are practical because they empede such behavior and keep the water clean for longer. Remember that a bird can survive some time without food, but will die without water very quickly. Always verify that the bottle or container is full and accessible.