Macaw behavior

Question
Why does my 1 yr old Military Macaw chew his feet and ankles?

Answer
-- It depends.  How long has this been going on and is he doing it to the point of any injury, sores, redness, oozing or bleeding?

How often does he do it?

What is the environment like that he's in?

Any other birds or animals in the home?

Whatever details you can offer will be helpful