Furthermore, lawns represent an ecological dead space. No birds nest there, few insects find harbor between the short blades of grass. Small mammals, snakes, frogs, salamanders, all have to look elsewhere for homes. The only good thing about a lawn is that if you're stuck with one (like I am) it's easy to care for if you reduce your maintenance to the bare minimum. I mow the lawn once a week during the growing season (spring and fall), and that's it. No chemicals, no watering. It's a heck of a lot easier to care for than any other gardening area, believe me!
However, now that I have chickens, I find that I am becoming far more concerned with lawn care than I would ever have thought possible. My lawn has changed categories, from "ground cover" to "crop for grazing animals." Grass is good for chickens, providing roughage, vegetable material, entertainment, and valuable nutrients. And the more grass they eat, the less feed they eat - which is pretty great, because I don't have to pay for grass.
Lawn care enthusiasts might be a bit startled by the picture on this post. I just want to warn you to be prepared. I have outlined the chicken tractor's path with yellow, so that you can more easily see the boundary.
The chickens are very... thorough... with their attentions. I move the tractor every day, so this represents only 24 hours of chicken love. As you can see, they pretty much eat every single green thing beneath them, which exposes how patchy the grass really is. Stripped of its green cover, it's easy to see the bare patches of ground and thatch which were previously hidden. In several places they have scratched up the soil for dirt baths.
This all looks a little scary, but the amazing thing is that it all grows back within a week. Within two weeks, you would never know that the chickens had been there. In fact, thanks partly to the "fertilizer" they leave behind, it grows back even more lush than it was before.
Grass evolved to be cropped by grazing animals. We mimic that cropping when we mow. When grass loses a small amount of leaf mass, it pushes its efforts into growing better roots. This in turn allows it to support more, better leaf growth. When chickens are allowed to graze a patch of grass, and it's then given at least a week to rest (depending on the season and growth rate), the grass comes back better than ever.
The high nitrogen content of chicken manure is an outstanding nutrient for lawns. However, it can burn the grass if it's left in place. After I move the chicken tractor, I soak yesterday's patch with the hose, being sure to break up the manure and dilute it away.
Naturally, if you are grazing chickens on your lawn, you will need to stop using lawn care chemicals altogether. The only thing that should go on your lawn is water and chickens, PERIOD. Fortunately you won't need fertilizer, and the chickens do an amazing job of weeding - clover and dandelions are big favorites with chickens.