Clemantis is toxic, if they eat it. That's why I mentioned how it can be managed with less risk. There are many toxic plants out there, and generally chickens avoid them if they have lots of other choices. Fortunately.
Mary
Clemantis isn't edible, but has been safe as decoration on the run fence if there are lots of other edible choices available. In other words, if the birds can free range a lot, and have more to eat than that clemantis.
Do be prepared for the weight and management of vines like grapes!
I have...