My Timneh has perches available varying from 1/2 inch to 2 inches. He sleeps on a concrete perch that is about 1.5 inches in diameter. That is his choice. However, when I got him someone here on the forum told me they tend to sleep on the highest perch available. So, I put the concrete one up there to help with nail grooming and sure enough, that is the one he sleeps on.