Rub cavity of duckling with salt, pepper and thyme.
Stuff with a mixture of the sliced oranges and apples, crushed bay leaf and parsley.
To close cavity, sew or skewer and lace with cord.
Place duckling on a rack in roasting pan and set in a slow oven (325F or 160°C).
Roast about 2 1/2 hours, basting frequently with a blend of 1/2 cup (1/8 liter) of the orange juice and the melted butter.
Spoon off the fat occasionally from roasting pan into a bowl.
When duckling is tender and well browned, remove to a heated platter and keep warm.
If needed, return some of the drippings in bowl to roasting pan.
Add the wine and remaining orange juice.
Bring to boiling, stirring to loosen drippings from bottom of pan.
Add very finely cut strips of orange peel and mix well.
Thicken the sauce with cornstarch blended with several tablespoons cold water, cooking and stirring until smooth.
Pour sauce into a gravy boat.
Garnish the roast duckling with mandarin orange sections or with orange slices broiled with butter.