If you're using hoops on standard 4-foot beds, chickens can be profitably integrated into the garden--depending on how many hoops you're willing to bend. A few months before planting, hoop a bed, cover the hoops with netting, put the chickens inside, and let them plow it, fertilize it, and deweed it for a week or two. 
Assuming you have other means of predator control--as in fencing the whole garden--you can run things this way all year: hooping in chickens on beds to be later planted; hooping out chickens from beds that are planted, and giving them the run of the garden out_side_ the hoops. You'll have to cover the hoops with netting, of course, but this goes on quickly with zipties, and the netting works nicely to support, say, spun fabric or plastic if you're over-wintering crops.
So the hoops work to either include or exclude the chickens, depending on your goal of the moment.
In the autumn, you could let the chickens have the run of the whole garden, excluding them only from your hoop-protected winter beds (parsnips, spinach, etc).