Albinism in birds - AbsoluteAstronomy.com

Albinism in birds is rare, occurring to any extent in perhaps one in 1800 individuals (Terres 1980). A bird that is albino

Albinism

Albinism is a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin...

(from the Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

albus, "white") has white feather

Feather

Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...

s in place of coloured ones on some portion of its body. A bird that is naturally white, such as a swan

Swan

Swans, genus Cygnus, are birds of the family Anatidae, which also includes geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae...

, goose

Goose

The word goose is the English name for a group of waterfowl, belonging to the family Anatidae. This family also includes swans, most of which are larger than true geese, and ducks, which are smaller....

, or egret

Egret

An egret is any of several herons, most of which are white or buff, and several of which develop fine plumes during the breeding season. Many egrets are members of the genera Egretta or Ardea which contain other species named as herons rather than egrets...

, is not an albino, nor is a bird that has seasonally alternating white plumage

Plumage

Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...

.

Four degrees of albinism have been described. The most common form is termed partial albinism, in which local areas of the bird's body, such as certain feathers, are lacking the pigment melanin

Melanin

Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...

. The white areas may be symmetrical, with both sides of the bird showing a similar pattern. In imperfect albinism, the pigment is partially inhibited in the skin

Skin

-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

, eye

Eye

Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...

s, or feathers, but is not absent from any of them. Incomplete albinism is the complete absence of pigment from the skin, eyes, or feathers, but not all three.

A completely albino bird is the most rare, lacking any pigment in its skin, eyes, and feathers. The eyes in this case are pink or red, because blood

Blood

Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

shows through in the absence of pigment in the iris

Iris (anatomy)

The iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupils and thus the amount of light reaching the retina. "Eye color" is the color of the iris, which can be green, blue, or brown. In some cases it can be hazel , grey, violet, or even pink...

es. The beak

Beak

The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...

, legs, and feet are very pale or white. Completely albino adults are very rarely spotted in the wild. They are likely easier targets for predators because their colour distinguishes them from their environment. Falconers

Falconry

Falconry is "the taking of wild quarry in its natural state and habitat by means of a trained raptor". There are two traditional terms used to describe a person involved in falconry: a falconer flies a falcon; an austringer flies a hawk or an eagle...

have observed that their trained birds are likely to attack a white pigeon in a flock

Flock (birds)

A flock is a group of birds conducting flocking behavior in flight, or while foraging. The term is akin to the herd amongst mammals. The benefits of aggregating in flocks are varied and flocks will form explicitly for specific purposes...

because it is conspicuous. A complete albino often has weak eyesight and brittle wing and tail feathers, which may reduce its ability to fly. In flocks, albinos are often harassed by their own species. Such observations have been made among red-winged blackbird

Red-winged Blackbird

The Red-winged Blackbird is a passerine bird of the family Icteridae found in most of North and much of Central America. It breeds from Alaska and Newfoundland south to Florida, the Gulf of Mexico, Mexico, and Guatemala, with isolated populations in western El Salvador, northwestern Honduras, and...

s, barn swallow

Barn Swallow

The Barn Swallow is the most widespread species of swallow in the world. It is a distinctive passerine bird with blue upperparts, a long, deeply forked tail and curved, pointed wings. It is found in Europe, Asia, Africa and the Americas...

s, and African penguin

African Penguin

The African Penguin , also known as the Black-footed Penguin is a species of penguin, confined to southern African waters. It is known as Brilpikkewyn in Afrikaans, Inguza or Unombombiya in Xhosa, Manchot Du Cap in French and Pingüino Del Cabo in Spanish...

s. In a nesting colony of the latter, three unusual juveniles—one black-headed, one white-headed, and one full albino—were shunned and abused by companions.

Albinism has been reported in all order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

s and in 54 families

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

of North American birds. The American robin

American Robin

The American Robin or North American Robin is a migratory songbird of the thrush family. It is named after the European Robin because of its reddish-orange breast, though the two species are not closely related, with the European robin belonging to the flycatcher family...

and house sparrow

House Sparrow

The House Sparrow is a bird of the sparrow family Passeridae, found in most parts of the world. One of about 25 species in the genus Passer, the House Sparrow occurs naturally in most of Europe, the Mediterranean region, and much of Asia...

led bird species in the incidence of albinism. Albinistic white appears to replace brown pigments more often than red or yellow ones; records suggest a greater incidence in crow

Crow

Crows form the genus Corvus in the family Corvidae. Ranging in size from the relatively small pigeon-size jackdaws to the Common Raven of the Holarctic region and Thick-billed Raven of the highlands of Ethiopia, the 40 or so members of this genus occur on all temperate continents and several...

s, raven

Raven

Raven is the common name given to several larger-bodied members of the genus Corvus—but in Europe and North America the Common Raven is normally implied...

s, and hawk

Hawk

The term hawk can be used in several ways:* In strict usage in Australia and Africa, to mean any of the species in the subfamily Accipitrinae, which comprises the genera Accipiter, Micronisus, Melierax, Urotriorchis and Megatriorchis. The large and widespread Accipiter genus includes goshawks,...

s than in goldfinch

Goldfinch

Goldfinch may refer to any of the following species of bird from the genus Carduelis:* American Goldfinch, Carduelis tristis* European Goldfinch, Carduelis carduelis* Lawrence's Goldfinch, Carduelis lawrencei...

es or oriole

Oriole

Orioles are colourful Old World passerine birds in the genus Oriolus, the namesake of the corvoidean family Oriolidae. They are not related to the New World orioles, which are icterids and, belonging to the superfamily Passeroidea songbirds, are quite unrelated to the true orioles.The orioles are...

s.

Abnormally white feathers are not always due to albinism. Injury or disease may change their color, including dietary deficiencies or circulatory problems during feather development. Aging may also turn a bird's feathers white.

See also