The position of a cockatiel’s crest feathers can tell you its mood. Straight-up crest feathers can mean the bird is startled or highly curious. A defensive cockatiel will hold its crest feathers flattened close its head, and it might be especially stressed if it also hisses.
Cockatiels are more inclined to whistle than talk. Male cockatiels are more likely to talk than females, and some can learn to speak a few words or phrases. Cockatiels tend to chirp rather than screech, and their relatively lower noise volume makes them a good apartment pet.
It is normal for a cockatiel to sneeze a few times a day to clear out dust or dander from its nares, which might be accompanied by a clear discharge. If the sneezing is persistent and/or the discharge is not a clear color, contact your avian veterinarian.