If the breast bone protrudes the bird may have a illness. Look at the vent area. It should be clean, and not have any stains. A bird with feces around its vent may be sick. Look for any missing toes.
Younger birds have soft feet, and older birds have slightly scaly feet.
However excessive scaliness is not a good thing, this could mean the bird has a vitamin deficiency. Look to see if the bird is banded. The band may tell you the year it was born, or help you find out by looking in a band registry. Another way to tell if the bird is young or old is to look at the beak and feet. In a young bird the beak and feet are smooth and soft, older birds have beaks and feet that show wear.