Melt 1 1/2 teaspoons butter over medium-high heat in a medium saucepan. Add shallots; sauté 1 minute. Add port, jelly, vinegar, and sugar; cook 2 minutes or until sugar dissolves. Stir in cranberries and cherries; cook 2 minutes or until slightly thick. Remove from heat. Stir in remaining 1 tablespoon butter, 1/4 teaspoon salt, and 1/8 teaspoon pepper.
While sauce cooks, heat oil in a medium nonstick skillet over medium-high heat. Sprinkle duck with remaining 1/2 teaspoon salt and remaining 1/8 teaspoon pepper. Add duck to pan; cook 4 minutes on each side or until desired degree of doneness. Serve with sauce.