Lorikeet sits at the bottom of the cage a lot, is he sick?

Our rainbow lorikeet (previously wild, found injured on the road as a baby, estimated maybe a year old now) has taken to sitting at the bottom of his cage. We've taken him to a regular vet and an avian vet when we first found him, a few months ago, and they said he appears to be healthy. He seems to have no problem climbing onto the highest perches to eat or drink and he seems to still be playing with his toys towards the top, just quite often he goes to the bottom to rest and groom. When he sits at the bottom he chirps and chatters and squawks like he normally does, often sitting there grooming himself. In other words he SEEMS normal, but we can't figure out why he'd want to sit on the metal cage floor instead of on one of his branches. He normally goes up onto a perch to poop. When we take him out of the cage to play on top of it or with us he seems to act normal. Someone suggested that sitting at the bottom of the cage is usually a sign of serious illness, even if the bird appears normal. Are we likely to have a sick bird or is our rainbow lorikeet just weird?

The guy in the photo below lives in a very large cage and he spends a lot of time on the floor of the cage. He will walk on the floor outside his cage sometimes also. Birds use altitude for safety. It's probably that he is beginning to feel secure in his cage. A good test of that theory is to watch what he does when a stranger, a dog or cat comes in the room.

It could also have to do with heat. It is most likely warmer high in his cage and he could find the lower altitude more comfortable. Unless he is lethargic or shows other signs something might be wrong, I wouldn't worry about it.