Remove the giblets and necks from the cavity. Reserve the neck to make duck stock. Rinse the ducks inside and out. Pat dry thoroughly with paper towels. If you have time, let them air-dry for 20 minutes (or overnight in the refrigerator). This will make for crisper skin.
Preheat the oven to 425 F. Sprinkle the duck(s) with salt and pepper, inside and out. Sprinkle the outsides lightly with cayenne, if desired. Tie the legs together with cooking twine.
Place the duck(s) breast-side up on a rack in a large roasting pan (this minimizes absorption of rendered fat). Roast the duck(s) for 15 minutes, reduce the oven temperature to 350 F and roast for another 70 to 75 minutes for medium–rare meat, or until juices run rosy when pierced with a fork (for well-done duck, roast until juices run clear).
When ducks are cooked, carefully transfer them to a platter, remove the cooking twine, and put them into the warm oven (which has been turned off) while you prepare the sauce. (The duck may be roasted in the morning, if desired, and reheated later at 300 F) If crisp skin is desired, place ducks under a broiler for 3 to 5 minutes.
Skim most of the fat from the pan (you may have almost a cup of fat), leaving behind the pan juices and about 2 tablespoons of fat. Add the marmalade, duck or chicken stock, and port. Bring the mixture to a boil and cook until reduced and sauce is thickened. Finish the sauce by adding a tablespoon or two of butter and cooking for a few minutes longer to give a nice glaze to the sauce.
To make quick duck stock: While ducks are roasting, simmer the reserved necks in 3 cups of chicken broth, covered, for about 45 minutes. Remove the necks and set aside the stock until you are ready to prepare the sauce.
Carve the duck(s) and arrange on a serving dish. Serve with duck sauce.
6 to 8