A day late, but (drum roll please) I announce that
@Bradders is the winner. Well done and thanks to all who took part.
An honourable mention goes to
@Kendra who was closest to what was actually going on. We would encourage Basil to come out of his cage by playing recordings of his own sounds. Where Head Boy Basil goes, the other three follow, so it got them all confident playing outside. Basil was fascinated with the speaker, trying to find the birds inside it.