It's never a good idea to mix parrot species in a cage. It sometimes works if you have a very large outdoor aviary. Budgies can be extremely territorial and aggressive toward other birds, especially those that are more docile in nature such as cockatiels. On the other hand, larger birds have larger beaks and can do serious harm to budgies. The risk of these problems is increased if you have birds that are nesting. If you are still planning on trying to mix two different parrot species, please be prepared to house them separately if it doesn't work out.