greenwing macaw face

Question
I am not very familiar with macaws, but I do share my life with a yellow nape amazon. Anyway, my brothers has a green-wing that i am feeding for him while he is on vacation. Well I was noticing that the white parts of his face have a yellowish hue. I don't know if its normal or not. I believe he is about 5 years old give or take. He seems to act fine to me though. Playful and excited to see me when i get there. Also I was wondering where i could find a good article about perches and and foot health for parrots. Specifically related to arthritis. He also has an african grey (congo) that i feel may have some feet issues. They just don't look quite right in my opinion and i know he never changes or rearranges its perches. He isn't the best parrot companion but now the worst either.

Answer
The yellow tinge would concern me as well.  If the bird is on a predominantly seed diet, hepatic lipidosis (fatty liver disease) is rather common.  The bird MUST be checked out by an avian vet, or at least a vet who is experienced with birds.

When it comes to overall bird care and even perch suggestions, check out www.4AnimalCare.org and click on the bird tab

Good luck and thank you for caring so much about this beautiful macaw.