Bill Diller, a photographer living in Huron County, Mich., had never seen a snowy owl quite like this.
In January, Mr. Diller’s neighbor told him about a “red-spotted snowy owl” in the area. It’s a part of Michigan known as “the Thumb,” which becomes home to many snowy owls in the winter.
People were calling the bird “Rusty.”
“I had never heard of such a thing,” Mr. Diller said, “so I figured either he didn’t know what he was talking about or this was some kind of exotic bird from Asia.”
When he soon shared pictures on Facebook of the eye-catchingly orange bird perched atop a utility pole, he helped create a feathered phenomenon. The discovery has perplexed avian experts, too, creating an enduring mystery about what might have made a white bird turn bright orange.
Julie Maggert, a snowy owl enthusiast, heard of Mr. Diller’s sighting and became determined to see “Creamsicle,” as she affectionately nicknamed the bird.
She made a series of visits over several days from her home in Central Michigan with her Nikon Z8 and a zoom lens. After hours of waiting at a respectful distance, she finally got the perfect shot of the tinted bird on a telephone pole.
“My adrenaline was going crazy, I was so excited!” Mrs. Maggert said.
Her pictures helped make the case undeniable: The bird shared a color scheme with the planet Jupiter or a clownfish. But why?
Scientists who have studied owls for years struggled to explain the bird’s curious plumage.
“In over 35 years of study, we have found over 300 nests and banded over 800 chicks,” Denver Holt, director of the Owl Research Institute in Charlo, Mont., said in an email. “We have never seen any plumage aberration, or anything like what is in the photos of the owl.”
Kevin McGraw, a bird coloration expert and biologist at Michigan State University, shared a surprising hypothesis: The owl became orange as a result of a genetic mutation driven by environmental stress, such as exposure to pollution.
Dr. McGraw said in an email interview that samples from the bird were needed to test that and other hypotheses.
“We’d need to get feathers from this bird to understand the nature of the unique coloring,” he said.
Geoffrey Hill, an ornithologist at Auburn University and a co-author with Dr. McGraw of a book about bird coloration, shared his interpretation.
“It seems unlikely that it has spontaneously produced red pigmentation via a genetic mutation,” Dr. Hill said.
He said “the red coloration seems too red to be caused by” natural pigmentation. He added that “the pigmentation is not very symmetrical and appears on the parts of a normal snowy owl that are white.” He surmised that if the bird had a mutation, it would have changed the owl’s black patterns, or eumelanin, to orange, or pheomelanin. That is not how the bird was currently colored.
He believed it looked more consistent with the external application of a dye.
Scott Weidensaul, a co-founder of Project SNOWstorm, a volunteer snowy owl research group, also dismissed the mutation hypothesis. Additionally, his organization ruled out that the bird had been marked with dye from the United States Geological Survey’s Bird Banding Laboratory, which studies avian movements. It had been standard practice in the 1960s, before the advent of GPS transmitters, for snowy owl researchers to use spray paint to study migratory patterns.
Dr. Weidensaul offered his own suspicions about the bird’s hue.
“The most likely explanation is that it was de-icing fluid at an airport, since some formulations are that red-orange color,” he wrote in an email.
The closest airport to where the bird had been spotted, Huron County Memorial Airport, did not reply to a request for comment.
Mrs. Maggert, who saw Rusty or Creamsicle with her own eyes, is skeptical that the owl became orange through accidental contact with a dye or spray paint.
“The way that it’s on its body, I don’t know how it could just accidentally rub up against paint all up on the front of her face and head and back,” she said.
Unless someone comes forward and admits to pigmenting the snowy owl, there will be no effort to study the bird up close, and its rusty appearance is likely to remain a mystery.
Karen Cleveland, a wildlife biologist at the Michigan Department of Natural Resources, said that the state had been aware of the bird since mid-January. While the owl appears “healthy and well,” the state agency hasn’t publicized its presence to limit snowy owl chasers from potentially stressing the bird.
“The department has no plans to try to capture it for any reason,” Ms. Cleveland said, “so we’re unlikely to ever have a conclusive explanation for this coloring.”