No need to worry about naturals as i only put mine in a section of there on a week ago ,i find the stronger they are as long as they are out each day in a temp cage to see about ,at this stage i close the sliding doors with bob wires fitted at feeding time then cox them from outside with a brush shank to go through for there feed ,if they are not going in like rockets after the third night they are thick or being fed to much ,i then only after this stage let them out when they are ready to take to the sky's straight away don't worry if half disappear as they will all return find they fly and batch in half the time on this system ,good luck .