The ideal size for an aviary depends on the type and number of birds you plan to keep. As a general rule, the larger the aviary, the better, as birds require space to move and fly. A minimum recommended size for a small bird species is around 3 feet by 6 feet by 6 feet, while larger birds may require significantly larger aviaries. It is always best to research the specific needs of your birds and consult with an expert to determine the ideal size for your aviary.