Dark Colouring around my African Grey Parrot's Eyes

by Rachel
(Sheringham, Norfolk, UK)

Hello, My African Grey parrot recently flew away and was lost in the local woods for 2-3 days. When he was found he started developing dark circles around the outer corners of his eye area closer to where the feathers join. They also seem to be getting darker.
I should make it clear that we are not 100% sure that teddy is a male, if that makes a difference.

What could this be? I can't take him to our local vet be cause they do not deal with birds so I need to know whether this is something to be concerned about.

Hope you can help.
Rachel