The feathers of the American goldfinch appear yellow in color due to carotenoids.

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References

"The coloration of feathers can be caused by carotenoids (usually producing yellow, orange and red), melanins (usually producing brown, black and grey), other pigments (such as found in some parrot feathers) or by nano-scale reflective tissues (usually producing UV-blue, white and iridescent coloration; Gill 1995). Coloration produced by the latter mechanism is typically referred to as 'structural coloration.'" (Shawkey and Hill 2005:121)

Journal article
Carotenoids need structural colours to shineBiology LettersMay 16, 2005
Matthew D. Shawkey, Geoffrey E. Hill

Journal article
An experimental test of the contributions and condition dependence of microstructure and carotenoids in yellow plumage colorationProceedings of the Royal Society B: Biological SciencesSeptember 5, 2006
M. D Shawkey, G. E Hill, K. J McGraw, W. R Hood, K. Huggins

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Living System/s

Organism
American GoldfinchCarduelis tristisSpecies

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