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.
Some species have eyes that change color when the bird ages.
Senegals, African Greys, and Macaws have eyes that lighten when the grow older. Handle the bird. Now that you have looked the bird over, and are sure it does not show any signs of illness, it is time to buy the bird. Make sure you get the phone number and address of the breeder or store you bought the bird from. Ask for written instructions on diet, care, etc.