What Was that White Bird?

The first time I saw the white bird flying overhead, I thought I’d gone slightly mad because large white birds are not common in the Ligonier Valley. I was riding my bike on a rural road between two cow fields, a herd of black-angus eyeing me warily. I pedaled slowly, watching what I presumed was an exotic visitor, white birds of all sorts running through my mind: egrets and snowy owls, ibis and seagulls, whooping cranes, snow geese, and ptarmigans.

The next time, I turned around and rode in the direction I’d seen the bird fly. It soared across the road to a copse between the fields and I found it perched high on a tree limb, regal and sure of itself, easy to spot against bright green leaves. I stopped and marveled at its whiteness, thrilled to see what instinct told me was something special. I noticed this time that it had a few brown patches. The bird took off in a gentle glide, swooping up and down on the thermals, presumably hunting for mice. The third time, I got off my bike and walked across a field where it roosted like a beacon atop a largely leafless tree. But I didn’t get very far. It flew away, white on white against a cloudy sky.

I concluded the bird was a raptor of some sort because it flew like a red-tailed hawk, had a similarly shaped body, and was where red-tailed hawks are supposed to be — except that it was bright white. A gyrfalcon perhaps? I knew gyrfalcons were white, but that would be a rare winter visitor here and my sightings were in summer and fall. We have an osprey nest about six miles from here, but the bird I saw was whiter. What it resembled most was a white hawk, common in Texas and South and Central America. I was stumped.

After a good deal of sleuthing, I decided the bird must be a leucistic hawk — something I’d never heard of — indeed, a leucistic red-tailed hawk. Annie Lindsay, the bird banding manager at nearby Powdermill Nature Reserve, confirmed my final guess and told me a leucistic hawk had been reported in our area. “Good sighting,” she said. Such sightings are often heralded on the internet, from coast to coast.

In birds, leucism is a rare condition that causes an aberration in the pigment, or melanin, in their feathers. It is a general term for many types of atypical coloration not only in birds, but also mammals, fish, amphibians and reptiles. Unlike albinos, leucistic animals may have patches of color, their eyes are not pink, and the feet and bills are normal. Piebald horses, for example, are leucistic.

While I was thrilled by the color variation in the bird I saw, life in the wild can be extra challenging for leucistic creatures. Without camouflage, both predator and prey spot them more easily. Mating can be difficult because they may not be recognized by their own kind. Eyesight is often poor and skin more sensitive to light. Birds’ feathers can be weaker and flight hindered. They often die young.

Leucism has long been considered genetic, but scientists are now questioning whether environmental factors play a role in certain aspects of leucism, including a condition called progressive graying. An article in Birding suggested that toxins in Utah’s Great Salt Lake might have caused additional leucism in eared grebes. Nightjars that fed on berries around Chernobyl may have shown increased partial leucism, and blackbirds in urban areas could express more leucism than rural birds.

Allison Shultz, an associate curator of ornithology at the Natural History Museum of Los Angeles County, believes there are probably both genetic and environmental causes of leucism. “Anything that will change a bird’s DNA,” she said. Cancer-causing toxins that humans worry about are the same for birds, she told me; such toxins can affect a bird’s general health, including its ability to produce the right colors. Every time a bird molts and grows new feathers, melanin cells have the chance of being degraded by environmental toxins such as radiation.

Still, there’s much ornithologists don’t know about leucism in birds, so Shultz and Stepfanie Aguillon, a Stanford Science Fellow at Stanford University, have asked the scientific community to give as much attention to atypical plumage as birders do. In an article published in October in Ornithology, they wrote: “The fascination of the birding public with the brilliant colors and patterns of birds means sightings of individuals with atypical plumage receive extraordinary attention. We suggest that these sightings should receive equal attention from the scientific community, as they could further our evolutionary understanding of bird color and patterning.”

But to do that, they need our help. They’ve asked birders to become community scientists, to photograph unusual coloration in birds and post such photos to websites such as iNaturalist and eBird. Fill in the comments section too, Shultz requested, which will make finding anomalies easier. They’ve also encouraged the scientific community to give community scientists the credit they deserve, including authorship in scientific papers. “People are essential,” she said. ‘Without lots of eyes out here, we can’t know everything,”

I got lucky and saw a spectacular white bird that led me on a wonderful investigation, but it also made me understand that paying attention to atypical coloration in birds is yet another way I might help our declining bird population. And while the great sleuth Sherlock Holmes himself may never have investigated leucistic hawks, I’m going to give him the last word nonetheless. In Arthur Conan Doyle’s, The Adventure of the Blanched Soldier, the fictional detective said: “I see no more than you, but I have trained myself to notice what I see.” I’m going to take a cue from Holmes’s wise words and work harder to notice what I see — and in the process, I hope, assist ornithologists to better understand our beleaguered and quickly disappearing birds.