Preheat the oven to 425°. Crack the duck bones into small pieces, place in a heavy roasting pan and cook in the oven, turning once, until lightly browned, about 25 minutes. Add the onions, carrots and garlic cloves and continue to cook until brown, about 30 minutes longer. Scrape the bones and vegetables into a large heavy saucepan. Discard the fat from the roasting pan; place the pan over moderate heat, add 1 cup of cold water and bring to a boil, scraping up any browned bits from the bottom of the pan. Add this liquid to the pot along with enough water to cover. Bring to a boil over moderately low heat. Skim the surface and add the bouquet garni and white wine. Simmer, uncovered, for 30 minutes. Add the tomatoes and cook for 30 minutes longer. Strain the stock into a large saucepan, pressing on the vegetables and bones to extract all their juices. Skim off any grease from the top. Boil the stock over high heat, skimming occasionally, until reduced to 1 1/2 cups, about 45 minutes.