Exchange information about how to teach specific tricks to parrots. Most of these techniques should apply to all bird species. Share your success stories.
Even if they are fully weaned they can still resort to the begging behaviour... it's like and habit that sticks afterwards for a while. I've seen it in 2 or 3 of my previous juvenile cockatiels. Different bird I know but same family species.
All species differ, I dont think a cockatoo at 5 months which is still displaying begging behaviour would be abnormal as they mature later than smaller species. I dont know about cockatoos specifically but I know alot of the medium-larger species do tend to stay near mum and dad for longer than we allow them in captivity (I did read something specifically about congo greys along these lines but like I say they are all different), during this time they will recieve the odd feeding and display the begging behaviour, probably most times they wont get fed though after weaning in order to teach them independance but sometimes they will.The behaviour tends to fade out on its own, I haven't heard of many adult birds that still beg unless the behaviour is strongly encouraged.