I keep chickens and ducks for their eggs and feathers they shed. The litter from the coop floor is a very important ingredient for the tilth of the 30x40 ft garden.
Previously the soil was sand and gravel forced to produce with the liberal application of chemicals. Since the addition of nitrogen rich chicken poop and the leaves,sawdust and straw I use for their deep bedding the tilth has vastly improved. The soil is rich and loamy with lots of worms.
When I rototilled the area this past spring I found a single worm in the 1200 square ft 'garden' area. Now the beds are full of worms, descendants of those I introduced. It gets watered even in these winter months so the critters in the soil don't dehydrate. I pick weeds and grasses for the birds and they lay eggs all winter. The symbionic approach really works well, the partnership between plants and animals assisting each other is basic and rewarding.