White birds have been reported at feeders across the eastern portion of the state recently. The birds are believed to be albino or partial albino juncos. Earlier this fall, some birders got some great photos of a partial albino red-tailed hawk, also in the eastern part of the state. A few years ago, I think it was 1995 and 1996, a partial albino robin nested in the same vicinity of Old Balsam Road two years in a row.
Albinism is a recessive trait and is quite rare. Albinos are often shunned in wild populations. Biologists believe albinos are alienated by their own species in an instinctive drive to preserve the integrity of the gene pool. Prey species may shun albinos as mates because their albinism makes them more easily noticed, thus attracting predators.

Albinism is the absence of melanin. Melanin is the pigment responsible for coloration. There are four types of albinism: Total - a complete absence of melanin. The melanin is not only missing from the skin but also from the eyes and hair. This is the rarest form of albinism. Incomplete - some, but not all, melanin may be missing from some or all of the skin, eyes and/or hair. Imperfect - melanin is present but only in small amounts. Partial - melanin is absent from only certain areas.

Partial albinism is the most common form. It, however, is still quite rare. A study done in 1936 concluded that albinism in any form was present in only one-half of one percent of the avian population. A 1995 study noted that albinism had been recorded in 304 of the more than 700 species of North American birds.

Since the browner pigments are generally the ones more affected by albinism, albinism is more common among darker species. Blackbirds, crows and robins are more susceptible than cardinals, goldfinches and other brightly colored birds.

The American robin is the most common of all avian albinos. According to studies, 8.22 percent of cases of avian albinism are robins. House sparrows also appear to have a (relatively) high incidence of albinism.

It appears that albinism is more prominent in social birds and/or birds that don’t migrate. Since it is a recessive trait it would be more pronounced in a setting where there is a greater chance of inbreeding.
Red-tails are the most common and wide spread of the buteos and albinos are often reported. Some reports are confusing because there is a white “morph” form of red-tail that often strays from its usual Great Plains home. This bird, called the Krider’s red-tail, is very pale with a whitish tail.

Albinism may not be as much of a limiting factor in predators as it is in prey species. Partial albino red-tails have been noted to inhabit the same territory for a number of years.

Patches of white feathers can appear on normally colored birds because of injury, dietary or circulatory problems or other physiological disorders. White feathers may suddenly appear on dark birds such as crows due to some type of sudden stress or shock.

 

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The Smoky Mountain News