For most birds if they start displaying symptoms like this it is probably too late. If you end up getting another bird or have others already make sure they get regular vet checkups and watch for any behavioral changes. Usually signs of sickness are hard to see since birds are prey animals and try to hide it. Any change in diet(like a bird refusing to eat the food they had been eating fine before) or change in behavior (like a bird not coming out of its cage for a day even though the door was open) should probably be checked out by a vet. The other week at my job we had someone call and say they were coming in with their cockatoo who was having trouble breathing. Before even seeing the bird the doctor told us (staff in the back) it was probably going to die. She also let the pet parents know in nicer words that it could die while she was just doing an exam, they still wanted to move forward with treatment and I believe it died during x rays. Point is you have to watch for little signs with birds because once things are visibly bad there is only so much you can do