Goats,like deer, are browsers, and prefer leafy vegetation, although, like deer, they will graze from time to time. Sheep are like elk. They like to graze, and are fairly particular about it, though occasionally, like elk, they will chew on brush and such. Goats are probably better backyard livestock because they will eat just about whatever is available, whereas sheep will not do without grass for long unless you give them pellets or hay. Goat milk is far more preferable than sheep milk, unless you have a Riccota fetish. Ducks and geese will take your grass right down to the roots, but are damned hard to milk. Duck eggs are much richer than chicken eggs. Ducks and geese almost always need a water source, like a pond, a pool, or at least a watering trough.