Cattails in autumn are what I'm used to, but in a much wider, diverse marsh. I'll have to keep an ear out for that particular clatter - I know the sound you're talking about - the next time I'm up around there.

Most of our marsh boardwalks are railed, between the wanting to keep people from jumping or falling in and the desire to protect a designated national wildlife refuge! I'll see if I can find a non-railed one.