Hello, Tweeters.

The amount of red coloration in house finch plumage comes from carotenoids present in their diet of seeds, fruit, and flowers. The amount and quality of these carotenoids injested during the period of feather development (post breeding) determines the degree of redness in their plumage. The less carotenoids, the less red the plumage resulting in orange and yellow variants. Thus, yellow or orange males may develop red plumage in subsequent years depending on their diet. Therefore, it is not age related, but entirely diet determined.

Jeff Kozma
Yakima, WA