Oh Hannah, that's so hard on you! Really, even after all this time, the decision is still yours and you'll have to make it, either now or at some time in the future. I guess the proper advice would be to allow Sunny complete freedom and do nothing until 'something' happens. Either he'll leave for good or he'll continue visiting you until you leave.
Hi Betrisher!
Sorry for the delayed response. It really is hard yes! I do think my best and almost only option is just wait and see what happens within the next few weeks, He has nothing stopping him from flying off and doing his own thing, I’m sure the more he matures the more he’ll want to spend time with the flock..hey he may fall in love with a gorgeous Corella and choose her over me 
My suspicion all along has been that Sunny has imprinted on you and sees you as his Mum. No matter how much fun he has with the wild flock, he still comes back to you. The worrisome part is that he doesn't have the proper fear of human beings and their machinery. He looks to humans for food and protection. Perhaps not every day, but often enough that he expects it when he comes. The crunch will be if/when
you leave. What might happen to Sunny then, especially if he's hungry, thirsty or sick?
Part of the decision to allow him to be wild and free is that you will be exposing him to all the diseases, parasites and injuries common to wild corellas (remember: PBFD is rife among wild Australian parrots). It has to be said: his life will definitely be much shorter as a wild bird.
On the other hand, you don't need to enclose Sunny in order to keep him. You just need to decide that you will commit to being his person and not simply leaving him without warning or preparation. If Rosetta's any yardstick, Sunny will cry for you if you go. He just will. It's not your fault (none of this is) but it's just the way Nature made it all turn out. If you hadn't come upon him, Sunny wouldn't even be here now!
I think the fact that he's had human intervention in his life has changed Sunny's prospects. I'm a biologist by training and logic tells me you should pack him off to the wild flock and then hide from him until he leaves and doesn't come back. HOWEVER, I have a living, breathing corella in a corner of my heart and I could never give that advice and mean it. Bottom line: you have to decide whether you want to ensure a long, healthy life for Sunny somewhere in your near vicinity, or whether you want him to have a shorter but more 'natural' one living exclusively with a flock and away from human companionship.
If he still sees me as his Mum then hopefully there is a chance he will ‘out-grow’ me? And want to leave. As long as he doesn’t see me as his mate..then it will be a problem as he won’t want to leave!
It is a worry that he’s quite tame, he doesn’t usually go up to random people and if the go to him he bites them lol. But he’s still tame. However if he leaves this years mating time I wouldn’t be too worried as I think he would forget people and be more wild when/if he returns next year.
His life would be shorter in the wild I know, but it would be a free, full and true to nature life, just how his real mum intended his life to be. He was born wild therefore I’m prepared for him to die wild. (I say that with a lump in my throat, holding back tears). If he continues to live like he does now for the rest of his life (half wild/half domestic) I will provide him with Vet care as soon as I notice something wrong.
PS. When making your decision, you don't need to overlay human emotions onto your bird. He won't 'miss' you in the way a human child would miss its parent. Rather, he would search for you expecting you to return as any other corella would to the flock. (Oh Lord, 'Setta searches for me! LOUDLY!) If you caged him, he would very quickly become used to that reality because it's what animals do. Otherwise, the stress of enclosure would cause widespread death among all our fids. It's why we all go to such lengths to provide good, worthwhile occupation so the birds feel busy and fulfilled. It's all up to you in the end, though. It's whether you want the responsibility (and pleasure) of having a corella permanently in your life. (NB. He's a lot smaller than a horse and his poo is negligible in comparison. He won't get colic or strangles and he doesn't need a farrier.)
good job she’s a sensible pony haha
