i have all my birds on open hole.yb season.i let yb,s out 1st then when yb,s have done their flying.i then let ob out .which get the yb,s back on the wing, i do reverse in ob season.works for me.i also have 3 cats and 2 dogs which stop most intruders.all my old birds will lift of roof and fly when i whistle.yb,s are just learning this. whistle then if birds dont take off i throw a ball up.the birds soon learn.by the time next year comes all no the score.