White Robin Sighted at Mackinaw City

This predominantly white robin has been seen by Mackinaw City residents. (Photographs by Tim Vieau)

Spring really is with us. Walking in the woods yesterday, I saw that the hepatica (liverleaf or May flower, as they're sometimes called around here) are blooming, and the trillium are up, although not blooming. Many migrating birds have begun to show up, either to visit or just pass through. One bird often referred to as a harbinger of spring is the American robin, which is interesting because through much of its United States range, it's a year-around resident. These songbirds of the thrush family (turdidae) are noted for their bold song, which is a gurgling, leisurely "sing-song cheerily cheer-up cheerio," which is often repeated. Because these birds consume earthworms, snails, and insects as a large portion of their diet (along with fruit), they're particularly susceptible to insecticide poisoning. Their decline in numbers in the 1960s, owing to the spraying of DDT in the 1950s, was instrumental in arousing concern over a potential "silent spring."

In addition to their song, American robins are probably best recognized by their bright, brick red breast, which contrasts nicely with their dark brownish gray back and wings, and their blackish head and tail. Once in a while, however, an American robin of another color appears. Recently, I had a call from Betty Vieau, who lives in Mackinaw City but works at our Tourism Bureau. In her yard, she observed a predominantly white, midsized bird with slightly rosy color on its breast. After talking with her neighbors, she found out that the bird had first been seen by Nelson LaPointe, also of Mackinaw City. Her 16-year-old grandson, Tim, took a picture of the bird and eventually Jeff Dykehouse, the naturalist of the Mackinac State Historic Parks, saw the photograph and identified it as a partial albino. According to one California study conducted over a 10-year period, about 17 in 30,000 birds have a degree of albinism.

Albinism is a condition in which an individual cannot produce a pigment known as melanin, and it can happen in birds, animals, and humans. It's a genetic condition in which an individual inherits two recessive genes. It doesn't matter what other genes an individual inherits for eye, hair, skin, or feather color; if the individual has those two recessive genes, no color will be expressed. This is what has been called an "inborn error of metabolism." In the case of albinism, an enzyme is missing in the system, the function of which is to convert tyrosine to melanin.

Totally albino birds not only have all white plumage, but they also have pink eyes, pale legs, and bills. It is twice as likely for a bird to be a "partial albino" than it is to be a total albino. Partial albino birds often have normal eye, bill, and leg color, and may well have patches of colored feathers. Partial albinism is sometimes caused by the failure of pigment to reach certain feathers as they're growing, perhaps caused by a blocked gland. Shock, unbalanced diet, disease, or injury may also cause partial albinism. Not all bird species have the same chance of having an albino individual. In a British article, "Albinism in Birds" (Bird Watch Ireland), researchers stated

that 160 species of British birds have been recorded to show albinism, either total or partial. Six families of birds seem the most susceptible to albinism, accounting for two-thirds of the albino birds recorded. These families include: thrushes (29%), crows (11%), swallows/martins (7%), sparrows (7%), starlings (7%), and finches (6%).

In North America, it has been reported that more than 300 species of birds exhibit at least partial albinism, although the frequency is still rather low; less than 0.1 percent of all birds. In the U.S., American robins and house sparrows have most commonly been reported as having partially albino individuals, although I've also seen articles about albino hawks and cardinals. It's interesting to note that bird species with red pigmentation often have that red pigmentation partially retained in the albino form, as is the case in the partial albino American robin that Betty found.

Partial albinos in the wild often have a difficult time surviving, and total albinos have difficulty in particular. Total albinos often have poorer eyesight and weak, brittle feathers that break more easily than normal birds. Because of the white coloring, they're sometimes not recognized, and ostracized, by their own species. If this happens, they're much more susceptible to predation, not only because of their white color, which makes them more visible against the greens and browns of the forest and fields, but because they're alone. They are therefore in more danger. Because of their coloring, they may also not be recognized as acceptable mates. This is not always the case, however. Betty said the robin she saw was hanging around with a couple of other robins who seemed to be keeping an eye out for him. In one report, a partial albino cardinal, who seemed to be associating well with other birds of his species, apparently had a mate. It was postulated that perhaps this was because he had the reddish tinges in the right places.

A number of other plumage abnormalities occur less frequently than albinism. Melanism is one of these. This is a condition in which a bird has an abnormal amount of dark pigmentation. In North America, this has been reported to occur in only about 29 species, including buzzards and woodcocks, as well as the most commonly reported melanistic bird, the pheasant. Erythism is a condition in which the bird has an excess of red pigmentation. Xanthochroism is a condition in which darker pigments are lost and there is an abnormal retention of yellow pigments. Some warblers and wagtails have been reported with this color deviation. Leucism is a condition in which birds are abnormally pale or washed out. This color variation is more common than the others, with the exception of albinism.

Trish Martin, a regular columnist for the Mackinac Island Town Crier, is a yeararound resident of Mackinac Island, has earned a master's degree in botany from Central Michigan University, and owns Bogan Lane Inn.