Ohhh Yes I actually found that yes it is recommended in an outdoor aviary.
This is from phoenixlanding.org "If you have an outdoor aviary, butterfly bush, snowball (viburnum), ••••• willow, forsythia or other parrot-safe vigorous hardy bushes could be planted in the aviary. By mid-summer these shrubs always need pruning. Give your birds a job! Grape vines are fun and safe. Tropical plants, hibiscus and palms, for example, can be set out during the summer in large pots in colder climates. Stand a large clay pipe on end, fill it with soil and add some greens. I can’t believe you ate greens! Last, but not least, have fun!" Lady Scarlett
I also read that the leaves themselves have high salt and vitamin A. I am never going to leave my birds alone in the Aviary so if they do go for the leaves i will make sure they don't over do it.