Ghosts on the Wing

In June of this year, I went birdwatching in Alaska, America’s last frontier and home to many birds you can’t see in the lower forty-eight. I was after the “lifers”—never-before-seen birds, as we birdwatchers say. I also wanted to see glaciers and mammals and to eat my weight in salmon and halibut.

After a week of Alaskan birding, I started to recognize some of the local birds that we had seen several times. While the group was visiting a bird feeder at a local’s home, I called out my identifications: “Pine Siskin, a Pine Grosbeak, a Common Redpoll, and a, um, a, wait, wait, a, what is that? I guess a redpoll with funky coloring?”

Such is the response to seeing leucistic or partially leucistic birds in the wild. In birds, leucism is a genetic mutation that doesn’t allow melanin, or pigment, to be deposited on a bird’s feathers. There are degrees of leucism, which depend on the extent of pigment loss and other genetic factors. Those birds that exhibit an equal reduction of pigment, or overall paleness, are called leucistic; those that have an absence of pigment in some feathers, but not all, creating white spots or streaks, are called pied or piebald birds (or partially leucistic).

Identifying these birds is confusing, especially for birders who use plumage color and markings for identification. Birds with unusual amounts of white coloring in their feathers also present a challenge to new birders, who typically don’t take into consideration body shape, habitat, location, and time of year. They often mistake the bird for an exotic species. One thing is certain … these birds don’t look like any of the pictures in the field guides.

Leucistic birds aren’t limited to Alaska or to any particular geographical area, for that matter. John Hartgerink, a retired engineer (and an excellent photographer) who volunteers at BREC’s Bluebonnet Swamp and Nature Center, said he sees partially leucistic Northern Cardinals at the swamp. Lucy, the Leucistic Cardinal, as one bird has been named, appears regularly at the swamp. This past fall, a leucistic Canada Goose was sighted with a flock near the pond on Woman’s Hospital’s campus in Baton Rouge. It was easy to see that this bird was the same shape and size as the rest of the flock but the color was mainly pale and it stood out like a ghostly apparition.

Leucism is not to be confused with albinism, another genetic condition that turns a bird’s plumage white or pale. The main difference between the two is that leucistic birds can show color in their feathers and have eyes that are black or another color, whereas albinism will manifest as no-to-little color and pink eyes. Leucism can also be mistaken in birds that are molting their feathers or that have suffered feather loss after a close call with a predator. Sometimes in these cases, the new feathers grow in white and then change back to the bird’s normal color at the next regular molt. This kind of temporary white coloring looks like leucism, but is not.

Leucism isn’t very common. Cornell’s Project FeederWatch collected data on plumage variations from the years 2000 to 2007, and only 1,605 unusual-looking birds were reported. This may sound like a high number, but given that FeederWatchers reports on 5.5 million birds each winter, this is a small percentage.

The abnormal coloring of leucistic birds can make them more vulnerable to predation from hawks and cats since they’ve lost their ability to use camouflage as a means of protection. Additionally, because color is so important in mating and courtship rituals, leucistic birds may not be able to find strong mates.

Leucism and albinism aren’t limited to birds; these conditions can occur in mammals and reptiles too. Many reptile breeders actually strive to produce albino snakes for the pet trade though finding them in the wild is unusual.

In Louisiana, the most famous leucistic reptiles are the white alligators housed at the Audubon Zoo in New Orleans. In 1987, fisherman noticed nineteen white hatchlings on Louisiana Land and Explorations’ property near Houma, Louisiana, and brought them to the zoo. Two of the original hatchlings, white gators with blue eyes, can still be seen at the zoo. One of the gators, Spots, who lived at the Audubon Aquarium of the Americas, recently died at 28 years old.

There have been two additional discoveries of wild white alligators in Louisiana, the only place that leucistic alligators have been discovered: A young female was found near Venice, and two young gators were seen near where the original clutch was first located near Houma. Leucistc birds are more common, but nature is unpredictable; and discovering one of her rarities is always intriguing.

For questions or comments, please contact Harriett at Harriett.pooler@gmail.com