In the winter of 2020–2021, a small group of Mallards hung around one of the wetlands at Fair Meadows. Among the ducks was one striking individual whose plumage stood out: a female with pale buffy and white feathers.
The female Mallard shows pale, buffy and white plumage (photo by Gary Shackelford).
Leucism is a condition caused by a genetic mutation that results in the loss of all types of pigmentation. It can affect the entire body surface or only patches—the affected areas can be either entirely white or a pale, washed out shade of the expected coloration. This is in contrast to albinism, a rarer condition that is caused by a complete lack of melanin, resulting in a totally white animal. One usually reliable way to tell whether an animal is leucistic or an albino is to look at their eyes. Leucistic animals retain normal eye color, whereas albino animals have pink or red eyes because the lack of pigment causes their blood vessels to show through.
Almost any animal can have leucism. Leucistic animals are intrinsically healthy, and they can survive if their lack of coloration does not interfere with their ability to avoid predators or attract mates.In leucistic birds, the abnormal pigmentation typically affects the feathers. Other body parts, such as eyes, bill, legs, and bare parts often have a normal coloration.
Our Mallard with unusual plumage had dark eyes and orange-red legs and feet, and her orange bill with a dark center indicated that she was a female (male Mallards have a yellow bill). We believe she could very possibly be leucistic, but because hybridization is common in ducks (both between wild species and domestic species), it is not possible to be fully certain. From what we could tell, she was similar in size and shape to the wild Mallards, behaved similarly, and appeared to be accepted as a normal member of the group. We saw them almost daily for about a month before they moved on.
White feathers on the rusty cap of a leucistic Chipping Sparrow (photo by Gary Shackelford).
Though leucism can occur in any species of bird, it is relatively rare. We have observed other leucistic birds at Fair Meadows, including a Chipping Sparrow with blotches of white feathers on its crown and a Barn Swallow with patches of white feathers on its back.
An interesting feature of leucism in birds is that it persists in the affected area of the body throughout successive molts. Several years ago, when we were living in St. Louis, we noticed a leucistic Common Grackle with a single white primary wing feather at our feeder during spring migration. That solitary white feather allowed us to recognize the same grackle returning to the feeder during migration the next two years. What a wonderful way to get to know an individual bird over time, thanks to this fascinating phenomenon created by Mother Nature!
Written by Gary Shackelford, Fair Meadows Sanctuary resident manager
Cover image by Gary Shackelford. A leucistic Barn Swallow displays bold patches of white plumage.
