Cardinals are usually associated with the bright red color of their feathers, but a couple in Illinois say a yellow version of the bird hangs out in their backyard.
Chelsea Curry told CBS News she first saw the yellow cardinal at her backyard bird feeder last year. At the time, she didn't know yellow cardinals even existed.
"Actually my husband kept telling me it was a cardinal and I argued that there was no such thing," Curry said. "That's when I Googled it and found out how rare it actually was."
Auburn University biological sciences professor Geoffrey Hill, who specializes in studying feather pigmentation, told CBS News he received the photos of the yellow cardinal from Illinois and confirmed that it is a male cardinal with rare yellow pigmentation. Hill was asked to verify the bird by the Chicago Tribune, which reported on the reoccurring spectacle in Rushville earlier this week.
Hill told CBS News he has seen photos of other yellow cardinals before, but the rare bird received widespread press in 2018, when one was spotted in Alabaster, Alabama. "That wasn't the first yellow cardinal, but that was the one that got national and even international press, and ever since, people have been aware of this and reporting on it more," he said.
Even though people are reporting on these birds more often, Hill expects that it's a less than one-in-a-million chance to actually spot one. "That was actually a quote I gave a reporter in 2018 — a one-in-a-million bird," he said. "But actually, it's probably a little rarer than one-in-a-million."
"There's only about 10 or 12 yellow cardinals in the eastern U.S. and eastern Canada in any given year, apparently there's about 50 million or more cardinals in that area," Hill said. Yellow cardinals have been spotted in several states, including Alabama, Florida, Ohio and Pennsylvania, according to Hill.
Curry said when people see her photos of the yellow cardinal they usually have a similar reaction to her original surprise. "[The bird] usually comes at least three times a day, but sometimes he will hang around most of the day," she said.
"The worse the weather is, the more he shows up," she said, adding that in February, the bird would spend the entire day in their backyard, eating at their feeders.
Hill explained that the yellow pigmentation of these rare cardinals likely comes from a genetic mutation. "This is a failure to convert carotenoids," Hill said. Carotenoids are yellow, orange and red pigments produced by plants and some insects that are then eaten by animals like cardinals.
"These [yellow] birds are not converting the yellow pigments they ingest in their diet to red. So, there's an enzyme that healthy northern cardinals have that allows them to convert the yellow dietary pigments to red plumage. And [yellow cardinals] don't have that — they don't have a functional version of that," Hill said.
"So presumably, it's a mutation, there was a change in the genetic code and the change caused that pigmentation system to fail," he said.
Hill told CBS News he hasn't seen a yellow cardinal in person, but he wasn't surprised to get a call about a yellow cardinal in Illinois. "It'd be like saying, 'Are you surprised to see this human blood disorder in Illinois, that we saw in these 15 other states?' And you'd say, 'No, there's people living in Illinois and this is a rare genetic mutation, and it can occur anywhere people live.' Same with Cardinals," Hill said.
He hopes any bird watchers who beat the less than one-in-million chance and see a yellow cardinal in person simply enjoy it: "Many bird watchers like me have spent a lifetime look at birds and never seen this. I've never seen a yellow variation of a red bird. All red birds essentially can show a yellow version just by having a mutation... And I've never seen that in any bird."