I'm trying to improve my poultry pen. It currently houses three ducks and I'll be adding several chickens, soon. I currently have only grass growing in there. I'd like to add some plants that will be nutritious foraging material for the birds and hardy enough to live through constant pecking. It would be an added bonus if they happened to look nice. I've heard that chamomile might be a good option - I've also been told to try butterbur (although I can't find the plants or seeds for sale anywhere)... any suggestions?