answer:Birds are fragile creatures. In order to protect the flock, sick birds are usually given a wide berth, even sometimes to the point that the other birds won’t interact at all with the injured/sick bird. The sick cockatoo most likely went back near the others, not close enough to rile the flock, and is sleeping. They won’t attack him, but they won’t help him either. I’m sorry your little feathered buddy is sick. Since he isn’t tame there is little you can do. You can leave food out for him- but the other birds will take it. Unless you have a way to capture the bird and get him to a vet, there’s not much you can do. That would stress the already sick bird and perhaps do more harm than good. You could try to make a ‘cozy’ for him and hang it near where he came to you most often. Fleece is good. They look like this to help keep him warm since his feathers are matted.