sleepy cockatiel?

by Anna L.
(Nebraska)

My 4-year old male cockatiel, Donny, used to be quite lively and spirited. He would sing, chirp, talk to feet (idk why, but it was cute) and just be an active and social little bird. But over the summer, Ive noticed that all he wants to do is sleep all day. He's hardly as active as he used to be, doesn't chirp in his cage much anymore and wont talk to feet.

He will climb up to your shoulder and preen, and later take a nap...and maybe wander the floor for about 3 minutes the fluff up to sleep. He now loves to be in his cage too, when it used to take us 10 minutes to coax him in there when he could fly (wings are clipped now.)

Is his change in activity due to being stuck in the cage for extended amounts--because of our move earlier this year/me not being able to take him to college/family cant get him out much when Im not home? I've tried to get him out as much as possible when Im home over the summer, but that hasn't helped much with his different activity level. Is his sleepiness a symptom of being cage bound, or might he be showing signs of illness? The silence is just so out of character for the little guy.....