chickens in moveable pens ("pastured poultry") are good for turning sod in to garden soil. they'll tear up the sod, especially if you are a little wasteful with food and just throw it down for them to scratch out.
They'll crap a lot, and that'll add a ton of nitrogen, which goes with your garden thread. meat and eggs from birds who are pastured have been shown to be more nutritious, and may save you feed money.

I've been cultivating 100'x8' wide strips for a couple years, planting cereal rye and winter wheat over the chicken pasture with great results.

the pens I have are 8x8x2 made of firring strips. chicken wire perimeter, but not on bottom. a piece of scrap tin covers half the top for shelter and shade. i hang a galvanized feeder and a gravity fed waterer plumbed to a 5 gallon bucket. with up to 6-8 birds, they'll need to be moved every other day. you want to move the pen before the crap "caps" the dirt. Unless you want bulk crap to shovel into a composter.

you can put any old box in there (I've used those brown recycling boxes, and an old dog crate) for a nest box if they're layers. if meat birds, they won't need a nest box.

if you want fertile eggs to hatch, add one rooster per 3-5 hens and if you have more hens, you may want 3 roosters. 2 roosters will fight, sometimes to the death. fertile eggs can be hatched in a homemade incubator, and will be a more 'sustainable' approach to buying eggs every year.

there're ways to determine if you have a lazy hen, one that's not laying. It happens, and they make excellent chicken enchiladas and stock.

couple weeks ago my biggest rooster got out and attacked me. Stuck him with my Sebenza and we had Coq au Vin for 2 days, and 4 quarts of stock for all kinds of stuff, including an excellent home grown black beans dish. it ain't city livin', for sure.

So there you go: pastured poultry, chicken tractors, fertile eggs, non-industrial meat.

btw, my 10/22 with carbon barrel, hogue stock, surefire and eotech gets used about twice a year for pest issues. I'd prefer my .223 with a can and safe backstop, but...

http://smallfarms.wsu.edu/animals/poultry.html
http://www.puyallup.wsu.edu/soilmgmt/SusAg_PasturedPoultry.htm
http://www.eatwild.com/products/washington.html