Beak Grinding in Parrots
Yes, what you are describing is very normal indeed. Most people, in fact, refer to it as "beak grinding". Birds often make this noise as they are settling down for the night. Often it occurs after the bird's cage has been covered and he or she is tucked in for the night. Sometimes this even occurs while the bird is perched on you perhaps taking a little nap. One theory I have heard is that the bird is in fact actually grinding his or her beak in preparation for the next meal, but most people believe this is a sign of contentment by a bird. Whatever the reason, beak grinding is a normal activity for any healthy bird.