The pigment on the secondary feathers of the cedar waxwing (Bombycilla cedrorum) is deposited as an amorphous layer upon a supporting medullary structure. The pigment was extracted with alkali and analyzed by chromatographic and spectrophotometric methods. The results indicate that the pigment is astacene (3,3',4,4'-tetra-keto-beta-carotene), the oxidation product of astaxanthin.
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Brush et al. (1963) studied this question.