Read a forum post once where a guy talked about using the old chimney flues for cable runs in houses like that. I mean, if the chimney isn't being used anymore, it's basically a giant empty tube going through the floors. Idk, seems like it could be a huge time saver if the layout works. Your gas line trick sounds way smarter than fighting with plaster and lath all day.

People cutting corners everywhere these days.

Have you tried matching the chirp to recordings on a bird website? I used to think it was all random noise, but learning just ONE call at a time completely changed my mind.