For the Birds Radio Program: Partial Albino Redpoll
(Recording of a Common Redpoll)
Two weeks ago, a partial-albino Common Redpoll came to my feeder. He was a beautiful little bird, with big white patches on his wings, a lot of white on his head and sides, a snow- white rump, and an all-white breast and back. The white was tinted with a very faint wash of pink, which made a pleasing contrast with the white snow. His crown was a redpoll’s typical ruby red, and where he did have normal streaking it was medium colored–not the shade of the darkest redpolls, but not light enough to make him a Hoary Redpoll.
I haven’t been able to find any examples of redpoll albinos in the literature, but that doesn’t surprise me. Bird- watchers and ornithologists are pretty much concentrated in the eastern and sunbelt states, where redpolls are only irregular invaders. So it makes sense that few people have ever seen albino redpolls. The most often-reported cases of avian albinism are in the American Robin and House Sparrow. But even albinos of these two species are extremely rare. Two ornithologists who banded fully 30,000 birds over a 10-year period managed to find only 17 albinos among them–that’s 1/2 of one percent. Adult albinos are much rarer than immature albinos, which is an indication that they tend to die at a young age. Falconers have often noted that their peregrines and merlins single out white pigeons in flocks–they’re probably easier to follow on high-speed chases. Also, pigments give feathers some of their structural strength. Even birds with naturally white plumage usually have heavy black pigments on the areas of feathers that get the most wear–like the black wingtips on seagulls and Snow Geese. Pure white feathers are often more brittle and subject to fraying than normally colored feathers. And the lack of pigments on albino eyes can affect the retina and lead to impaired sight, especially in bright light. Albinos are often harassed by their own kind, and may not be recognized by potential mates because of their odd color patterns. No wonder they have such a short lifespan.
Albinism appears to be caused in most cases by a recessive gene or genes, which cause a shortage or absence of the enzyme tyrosinase. The rarest result of this is total albinism–in this case, there is absolutely no melanin in the eyes, skin, or feathers. Partial albinism is more common. In this case there are white patches on the body, but other areas are colored normally. The white patches can be situated either symetrically, as in my bird’s case, or asymetrically.
In some cases birds develop white feathers as they age. Feathers can come in white after a bird is injured, as in a Red-winged Blackbird that received a shotgun wound on its breast. The feathers that grew in from the damaged tissue grew in pure white. And one Great-tailed Grackle developed a cyst on its cheek after a sliver became imbedded in its jaw. After the grackle molted, its cheek feathers came in white.
White feathers can also grow in after a bird receives a shock. When a cat frightened one European Blackbird living in captivity, it molted all its feathers, and the new ones grew in white.
As of April, 1965, albinism had been documented for 304 species of North American birds representing every taxonomic order. But individual albino birds are still rare and lovely jewels.
(Recording of a Common Redpoll)
This is Laura Erickson, and this program has been “For the Birds.”