Marilyn, That is a wonder he ate that since my Orchid Cactus has nasty thorns on it you can not even see. Everytime I move mine i get those suckers in my fingers since it it so big. Don't all OC have thorns maybe?
I can not imagine a cockatiel (maybe a cockatoo since they are so much bigger) being able to eat that without hurting his mouth. I guess if he was hungry enough he would eat it. My amazon will pick off any stems of plants that get too close to his cage and they do like to do that just for fun, he does not eat any of it, just tears them apart....... but those thorns are so nasty. Wow, dumb bird. Did he survive? I am curious, as a breeder of exotic birds, why did she want to have a cockatiel living in her greenhouse? Is that something new people do or what?
They could make a mess out of the plants, big time. Just normal for a bird to forage.