i have a hawk that sits on top of my coop in the morning i have 5 chickens araucauna mixed with rhode island reds or at least thats what my friend that i got them from tells me. the way that i took care of my hawk is that every morning id go out there with my pellet gun and just shoot it hard enough to scare it but not actually go into it. after a week and a half of that it just stopped coming by. as for the grass problem i just have a moveable coop and run i just move it to a new spot in my yard every day. good luck n sorry bout your hens