i now relise theres a lot of rubbish written about perches, size etc.... i always put a mix a various sizes, 2" - 4" branches and other sizes , various bits of wood slightly rounded, but my birds like to roost in laurel bushes so i now put a mix of branches in their shed now ive penned them in, when there manky burn them and replace with new. But i have sheds, trees , bushes, etc but a lot of them choose to roost on some metal barriers , the type the council put out along the street when theres and event on, also the top of builders security fenceing barries,they are metal and round, little grip but thats what they choose.