Eye Skin Pigmentation

[Ming-Ming]

I was curious if anyone knows what causes the darker coloured eyes, and lighter coloured eye skin pigmentation? I was told that it was genetics, and some have light and some have dark coloured.
I was also told that it could also be caused by sun exposure.

Here is Douglas at 8 months old...
Douglas' skin was actually pretty light when I got him...

And this is about...
5 months after that.

And 3 months after that...

And a picture taken last week.

I can't say I took him outside a lot, maybe about once or twice a week for an hour in the summer. But he is in front of the window now. Do you think that might have the same affect? Or it could be due to age?

Any ideas?

 

[TITANIS]

Well, it's hard to say on a species per species basis, but I know that some parrots like certain conures will get darker eye-ring pigmentation from sun exposure. That has also been stated for HH and makes sense because all the wild HH pics I've seen show dark eye-ringed individuals. There may be other reasons in addition to sun exposure such as diet. Age has also been cited but IMO has less evidence backing it anecdotal or otherwise, again depending on species.

 

[Ming-Ming]

Here are a few more pics I scrounged up.
These are some wild black headed caiques.

And white bellied...
(also looks like a yellow tailed!)

 

[TITANIS]

^ Love the second pic!

 

[Doodle Bird]

Hmm, interesting topic. I kind of prefer the darker color myself and always wondered about it. It could be sun, but I've met a few babies under 6 months who had super dark skin and had never seen the light of day. During the summer I take Nani out every week and haven't noticed any color change.