I have a 8-9 month old cockatiel. After looking up signs of illness because once he retured home from a friend's house during a vacation, I noticed he was sleeping a lot during the day and still does sometimes. It's since been a few months and now he is about the same as he was. Upon reading on these "signs of illness," I read that fluffed feathers and a sleepy look can also indicate a sickness. However, he's done that his whole life. His feathers are tight and his eyes are open when he isn't idle. He still sings as beautiful as ever and still loves to come out. I honestly think his sleeping problem is his fear of darkness. He is always alert at night and hisses when he can't see what's going on. Is anything cause of concern or am I just overreacting? Thanks!