Is my cockatiel being sick?

Hi there,

I have a one year old male cockatiel and he's been with me since he's 3-month old. He's been eating healthy and being very active. Today, he's still as active as always and eating as usual, I left the house for around 8 hours (I usually left him alone in the working days for this amount of time and he has lots of toys and I left the radio on) and I came home saw him sitting on the water bowl (which was the lower perch). Other than that he's fine and his droppings were all normal where he didnt appear to me that he's sick or anything. I put him to bed at 7pm and he usually sleep on his food bowl (which is upper on the cage) but just then he changed his spot on to a lower perch. I heard that if birds are sleeping down below then they are getting sick.

I appreciate if any one could answer my question, I am very worried.

Cheers