In a large stockpot, combine the bones, water, carrots, onion, celery, rosemary, sage, and peppercorns and bring to a boil. Reduce the heat and simmer for about 3 hours, skimming occasionally. Strain the stock. Measure 3 1/2 cups of stock for cooking the farro, and reserve any leftovers for later use. Preheat the oven to 350°F. Cut each of the game hens, chickens, or pigeons in half then season all over with kosher salt and freshly ground black pepper. In a large saute pan over moderately high heat, warm the oil. Working in batches, add the birds, skin side down, to the pan and sear until the skin is golden brown and caramelized. Transfer the birds, as done, to a roasting pan or large rimmed baking sheet and roast in the oven until an instant-read thermometer inserted into the thickest part of the thigh (do not touch the bone) registers 165°F. In a medium saucepan over moderate heat, cook the bacon until crispy. Transfer the bacon to a paper towellined plate and pour half the rendered bacon fat into a medium saute pan and set aside. Add the shallot to the original saucepan and saute, stirring occasionally, until translucent then add the farro and saute, stirring occasionally, until just toasted. Add the reserved 3 1/2 cups of stock to the farro and bring to a simmer. Continue simmering until soft and tender. While the farro is simmering, heat the rendered bacon fat in the medium saute pan. Add the mushrooms and saute, stirring occasionally, until the liquid released by the mushrooms is evaporated, about 5 minutes. Season with kosher salt and freshly ground black pepper. Add the mushrooms and bacon to the farro and stir to combine. Keep warm. In a small saucepan over moderately low heat, bring the olive oil, sage, and peppercorns to a simmer. Shut off the heat and let the oil cool until it`s fragrant with sage and peppercorn. Once cool, strain the oil. In small saucepan over moderate heat, bring the blackberries, currants, red wine, honey, and vinegar to a simmer. Continue simmering until the mixture is thick and jamlike, 8 to 12 minutes. Remove from the heat and set aside. Preheat the oven to 450°F. Arrange the fennel and carrots in separate baking dishes or baking sheets. Drizzle each with 1 tablespoon olive oil then season with kosher salt and freshly ground black pepper. Roast, turning occasionally, until tender and well caramelized, about 15 minutes. Transfer to a large bowl, drizzle with the maple syrup and vinegar, season with kosher salt and freshly ground black pepper, if desired, and toss to combine. Divide the farro among 4 plates, then top each with vegetables and poultry. Garnish the plates with the berry compote and sage oil.