When a white or almost white bird lands in your backyard, it’s tempting to automatically say that it’s an albino — once you’ve ruled out the unlikely great egret or snowy owl.
For avian color oddities, it’s a little more complicated than that.
Melanins and carotenoids are two of the three pigments found in birds. In addition to color (dark blacks through browns, red-browns, yellow browns and pale yellows), melanins provide strength and resistance to wear in feathers, more so than other pigments.
Carotenoids create reds and many yellows, but enter the picture by birds eating plants (or eating animals that eat plants) because carotenoids are synthesized in plants.
An absence of melanin or carotenoids would cause a lack of the colors that they produce.
Only it’s that not simple.
To say that ornithologists can’t agree on a clear definition of albinism or leucism (we’ll get to that in a minute) and degrees of albinism would be generous. If you care to be entertained, go to www.birds.cornell.edu and search for ‘leucism and albinism’ and choose the first entry. Don’t say I didn’t warn you.
For our purposes, let’s opt for this: Albinism in its purest form is the result of an absence of melanin, carotenoids and porphyrins, all pigments, so the bird’s feather color is white plus it has pale pink or reddish eyes, legs, feet and bill.
Partial albinism is the absence of melanin, which means that such a bird could be colorful because other pigments such as carotenoids cause red and yellow feathers, for instance. Some ornithologists argue that you can’t have a ‘partial albino.’
Leucism is reduced pigmentation in the feathers; birds can have patches of white and colored feathers, or washed out colors, but the pigment in the eyes are not affected, and usually the legs, feet and bill remain the normal color.
In either case, it’s the result of a genetic mutation. And while it is very unusual and interesting avian oddity, it can be dangerous for a wild bird.
Melanin is part of the structural integrity of a feather, and when it is missing, the lack can cause feathers to weaken and wear out more easily.
The lack of camouflage doesn’t allow the bird to blend in and a white or partially white bird stands out, making an easier target for predators.
Melanin also protects the eyes from damaging UV rays. Without melanin, birds’ eyes don’t function properly, and poor eyesight leads to a short life.
Colorful plumage during mating season is essential for attracting a healthy mate. Dull colors are not conducive to romance.
What’s important to remember is that — ornithologists parsing the definition of albino and leucism aside — birding should be enjoyable. Be excited when you spot the oddity. Follow your curiosity, and it’s an educational experience.
Wolves: A new two-minute animated short explores the splintered relationship between wolves and people. “The Fable of the Wolf,” released by Earthjustice, seeks to combat negative misconceptions about the species. See it at http://bit.ly/1LG5zsR.
Bullets: Popular hunting seasons for deer (modern rifle) and waterfowl are in full swing, so if you’re birdwatching in hunting areas, be aware. Consider wearing something that’s bright orange even if you don’t look like a deer or a duck. The Washington Department of Fish reports that more than 49 million ducks were counted on northern breeding grounds this spring.
Columnist Sharon Wootton can be reached at 360-468-3964 or www.songandword.com.
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