How Big Should the Cage Be?

This is Keifer, my young yellow collar macaw. He was originally situated in a cage that I thought was adequate for his size. The longer I had him, the more I realized that he required a much larger cage. Why? Because of his activity level and keen interest in everything! He spends a lot of time in my huge Exotic Enclosure 4' x 6' x 6'. He also spends a good portion of each day outside in a large outdoor flight cage. Is your bird's cage big enough? What activity level does your bird display? Is he/she all over the place? Does your parrot stay glued to the side hoping to get out and play? A little careful observation will help you determine your bird's needs.