AT many country fairs, draft animal contests are a popular draw. To the sound of cheering bystanders, horses or oxen vie with each other - prodded on by their master's whips - in pulling man-made weights the farthest and fastest.The Common Ground Fair, however, shuns competitive weight pulls for kinder demonstrations of farm animal capabilities. "We have contests, but the animals are doing what they were bred to do ... and working at the tasks they've trained to do on the farm," explains Nancy Ross, executive director of the Maine Organic Farmers and Growers Association. For example, horses and their drivers are judged on efficiency and coordination as they pull logs through obstacle courses. How well a horse moves and works with the driver is critiqued. Here, it's easy to gain appreciation of logging skills developed over centuries - and respect for the mammoth animals that respond to the slightest verbal command. "There're only a few of us working the woods like this," says David Littlefield, a logger from Belfast, Maine, who owns a homemade pulp loader driven by two huge Percheron horses. "You get more off the land with a pair of horses." Unlike modern machinery, a good pair of oxen "won't scar trees up, push 'em over, or tear up roots," says Dwain Chase, a part-time logger from Wilton, Maine. His two black and white Holsteins, Tiger and Lion, each weighs more than one ton and together can pull up to 6,000 pounds. Oxen take longer than machinery to clear woods, but they aren't as "messy," Mr. Chase says. Machinery leaves impenetrable thickets of leftover wood and brush. "Using animals," he says, "you end up with nice roads where you can t ake a Sunday morning walk." Chase makes his living as a carpenter. "At one time, about everybody ... kept about 10 to 15 pair like these 'cause they worked for a living in the woods. Now, it's mostly a hobby. ... I don't get rich on it, but it sure helps put groceries on the table."