So...tonight is my second attempt to leave my chicks in the coop all night long (first time was a failure...couldn't take the crying coming from them so I brought them back into the house). I know that they are supposed to return to the coop at dusk...but what kind of dusk are we talking about? When do I shut the coop door with them inside? When the sun has gone down, when it's almost dark, or when it's completely dark outside? Thanks!