Domestic poultry is almost always cooked well done (except squab and sautéed or grilled duck breast). Many cooks, however, cannot tell the difference between well done and overcooked. Chicken and turkey are low in fat, so they quickly become dry and unpalatable when overcooked. Even duck and goose, which are very fatty, taste dry and stringy if cooked too long.
Skilled chefs with years of experience can often tell the doneness of a roast chicken or turkey just by looking at it. Nevertheless, the only way to be certain of proper doneness is to use a thermometer.