I was away for a couple of weeks and while the birds ran out of provided deposit material during the first week, they didn't manage to bring anything of thier own after that. Visits declined as well, so I put some caps and butts out for them to resume their activity. I put some on the platform as well to try and entice them back.

So I'm still on Stage 4, will think about how to get to Stage 5 and try again.