Odd Blue Jay reported in Bangor last week

Leucism chiefly affects this jay's crest (file photo)

A Blue Jay that was seen in Bangor this past week was not quite as blue as it should be.

The jay had an unusual condition called leucism, which is an abnormal plumage disorder caused by a genetic mutation. Pigmentation cells in the feathers fail to develop properly. 

Birds with this mutation may have white patches where there shouldn't be any. Or, the plumage overall may be pale, making the feathers seem faint or bleached. In rare cases, the feathers are entirely white, with no discernible color.

The sighting of the leucistic Blue Jay was reported to Dave DeReamus, of the Eastern PA Birdline, which is sponsored by the Lehigh Valley Audubon Society. The bird was seen on January 15.

It's important to note that a leucistic bird is not an albino bird. There is a difference between the two genetic conditions, says birding writer Melissa Mayntz. Leucism affects only the bird's feathers. The bird may show some bright colors while other areas are pale. Only in extreme cases will all the pigment be lost, giving the bird a white appearance.

Edges of wing bars indicate this jay is not an albino

An albino bird has no pigment whatsoever in its feathers. Moreover, the genetic mutation extends to other parts of the bird. For instance, albino birds show pale pink or reddish eyes. The legs, feet and bill are pale. Leucistic birds have normally colored eyes, legs, feet and bills.

Leucism is most visible among brown and black birds. They lack melanin, which is deposited in the growing feathers by color cells. It's especially startling to see a leucistic crow with patches of white or plumage that is entirely pale!

Leucism has been seen among Bald Eagles, Hairy Woodpeckers, sparrows, starlings and Northern Cardinals. The condition even extends to animals with hair such as squirrels and giraffes. Aquatic mammals such as whales and dolphins may be affected too.

Pale crest and head on leucistic Blue Jay

Leucistic birds are rare not only because genetic misfirings are infrequent in general. These birds also face an uphill struggle in life. The fainter plumage robs them of protective camouflage. Hawks and feral cats have an easier time spotting them. Male leucistic birds may fail in courtship rituals because they lack the vivid coloration that females prefer.

Between 2000 and 2007, just 1,605 unusual-looking species were reported to ProjectFeederWatch, a program sponsored by the Cornell Lab of Ornithology. That's a tiny minority compared to the 5.5 million birds reported during each winter's bird count.