What is Bird Xanthochromism?
Bird Xanthochromism is a genetic mutation that results in excessive production of yellow pigment. This mutation is, in reality, related to the lack of production of the color red, which is replaced with yellow. Xanthochromic birds can have the bill and bare parts of the normal color or yellowish.
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Xanthochromism may be associated with other genetic mutations characterized by excessive production or deficiency of specific colors. Xanthochromic mutations result in a unique plumage on a bird according to the species’ normal coloration.
Xanthochromic birds in aviculture are deliberately bred to obtain and maintain the xanthochromic mutation or pure yellow birds. These birds are called lutinos.
Are there other causes of xanthochromism?
Xanthochromic individuals may result from dietary deficiencies. Carotenoids occur in plants and some animals, and birds uptake them as part of their natural diet. An example of the role of carotenoids and bird coloration involves flamingos. If deprived of the blue-green algae and brine shrimp rich in beta carotenes that give them their bright pink plumage, the birds become pale and whitish. By providing captive flamingos with a compound called canthaxanthin, the rich pink coloration can be restored.
Related: Bird Molting
Do all xanthochromic birds look alike?
Apparently not. Xanthochromism results in excessive production of yellow pigment and suppression of the red pigment. Depending on the typical species’ plumage where the xanthochromic mutation occurs, the resulting xanthochromic plumage could maintain some of the normal colors or dilute all colors to a yellowish tint.
Can xanthochromic birds be confused in the field?
Unlike white, in the plumages of albinistic and leucistic birds, the color yellow is a regular color in many birds’ typical plumage. Xanthochromic birds are less likely to be identified as abnormal by a casual observer.
Do xanthochromic birds have problems with having yellow plumages?
It is unclear whether xanthochromic birds are affected by an increased risk of predation, plumage deterioration, and physiological problems as albinistic and leucistic birds do.
Xanthochromism is widespread in aviculture. A Rose-fronted Lovebird (Agapornis roseicollis).
Is xanthochromism common among birds?
Exact numbers are not available, but only an approximation. Between 2000 and 2007, the Project Feeder Watch participants report approximately 5.5 million birds each winter. Only about 1,605 individuals were reported as having an abnormal plumage. This includes albinistic, leucistic, melanistic, and xanthochromic birds, among others. The number of birds with abnormal plumages represents approximately 0.01% of birds in the region these numbers were taken.
Related: Bird Plumage: Pattern & Functions
How to Identify a xanthochromic Bird?
Seeing a pure or part yellow bird in a habitat where such plumages are unexpected will call an observer’s attention. At first, such a different plumage may bring confusion, but at a closer look, one will likely arrive at the bird’s identity.
Xanthochromic birds are rare, but identifying them is relatively easy.
- See which birds are associated with the xanthochromic bird. If the xanthochromic bird has a normal color on the bill and bare parts, find similarities in birds the xanthochromic bird associates with. The xanthochromic bird is likely a member of the same species.
- If the xanthochromic bird is alone, see the habitat type, shape, and foraging behavior. These clues should give you an idea of which bird species occur in the area the xanthochromic bird is likely to be.
Related: A Guide to Bird Feathers
Conclusions:
Bird xanthochromism is a rare mutation that results in the yellow pigment’s excessive production and red pigment suppression. Xanthochromism can also occur as a result of dietary deficiencies.
Xanthochromism results in various plumages, which depend on the typical species’ plumage in which the mutation occurs. Some birds are pure yellow, while others only have some yellow feathers.
Birders rely on plumage as the primary clue for bird identification. An atypical bird plumage is likely to cause temporary confusion. Still, taking the clues suggested here, it is likely that you will be able to arrive at the correct bird identification.
References:
- Cornell University Project Feeder Watch.
- Wikipedia: https://en.wikipedia.org/wiki/Xanthochromism
- Isted, Deloris (1985). “A xanthochroism male Purple Finch.” Bulletin of the Oklahoma Ornithological Society. 18
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