Chickens, turkeys, and other meat birds are difficult to roast whole, because their two kinds of meat are best cooked differently. The tender breast meat gets dry and tough if heated much above 155°F/68°C. The leg meat is full of connective tissue, and is chewy if cooked to less than 165°F/73°C. So usually the cook must choose: either the leg meat is sufficiently cooked and the breast meat dry, or the breast meat succulent and the leg meat gristly.
Cooks try to overcome this dilemma in many ways. They turn the bird in various routines to expose the thigh joint to more heat. They cover the breast with foil, or with wet cheesecloth, or strips of pork fat (“barding”), or baste it, all to slow its cooking. They cover the breast with an ice pack and let the bird sit at room temperature for an hour, so that the legs start the cooking warmer than the breast. They brine the bird to juice up its breast. Perfectionists cut the bird up and roast legs and breasts separately.