I never thought about adding a mirror when isolating chicks! I have one with an injury, and I feel so bad cause she looks so lonely! I'm sure she will feel so much better with a mirror! Great Idea!
We put a thermometer in our brooder box that is mounted behind a pane of glass with a silhouette picture... the chicks keep seeing their reflection in the mirror and wondering how that other chick got back there. It's hilarious!