Xanthochromism
Xanthochromism is an unusually yellow pigmentation in an animal. It is often associated with the lack of usual red pigmentation and its replacement with yellow. The cause is usually genetic but may also be diet. A Cornell University survey of unusual-looking birds visiting feeders reported that 4% of such birds were described as xanthochromistic. The opposite of xanthochromism, a deficiency in or complete absence of yellow pigment, is known as
axanthism. Birds exhibiting genetic xanthochromism, especially deliberately bred mutations of several species of parrot in aviculture, are termed "lutinos". Wild birds in which xanthochromism has been recorded include Yellow Wagtail, Wood Warbler, Cape May Warbler, Rose-breasted Grosbeak, Evening Grosbeak, Red-bellied Woodpecker, Scarlet Tanager, Northern Cardinal, Great Spotted Woodpecker, Common Tailorbird, Crimson-breasted Shrike, Kākāriki and Kea.