Bruce,

Although I can't get into my cockatiel's heads to determine if they don't like a particular type of cage, I have to think about how I would feel if I were shut into a round room all day long. I think I would lose my mind! I also think it is easier for a cockatiel to climb in a cage that has corners and a square top.

My recommendations for a cage would be 3/4" or smaller spacing between the bars, a nice large door that will accommodate your cockatiel on your hand, and at least two sides of the cage having horizontal bars. The cage should no smaller than 18 inches square, especially if you plan to have toys in with your cockatiel.

Hope this helps!