I don't know how high he could get, because I have him in an adapted coalshed, with netting on the roof and door, and it's only about 4 feet high. He can easily get up to the roof of that, and cling on to the netting, but I don't know if he could get as high as a tree. He practically has a heart attack when anyone goes near him to feed him or anything, and he is clearly miserable, so the sooner I can let him out the better. We are in the middle of London, so cat free areas are a problem here. There are also loads of foxes.
He still has almost no tailfeathers, and very few of the long wingfeathers.