I haven't hunted anything with them. I'm sure the wooden darts would be capable of it but I wouldn't trust the wire ones. They were mostly for fun. If you want to hunt small game with a blowgun you can split an exacto razor head and glue it to the front of your wooden dart to make a broadhead.
I'm not sure how cattail would hold up but the thistle seed seems to hold up well. You split the dowel at one end and tie one end of a two foot piece of thread to it. Holding the thread in your teeth and the thistle seed in your right hand you then spin the dart slowly with your left hand as you fletch with the seeds you flatten into a bunch with your right hand. I wish I had a picture tutorial to share, it would be much easier to describe. I haven't found any suitable thistles around here yet.