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ERIE, Pa. – Longtime birder Jamie Hill knew he'd come across something rare.
The Waterford, Pennsylvania, man saw a northern cardinal that appeared to be male on its right side and female on its left.
"It was one of the experiences of a lifetime," Hill said about the bird that was bright red like a male cardinal on one side and brownish white like a female on the other.
Known as a bilateral gynandromorph, he described it as "a bird divided right down the middle, half male and half female" that stood out as "pretty unusual." Hill photographed the cardinal Saturday in trees behind a residence in Warren County, Pennsylvania, about 55 miles southeast of Erie.
He'd been alerted to it by a friend of the homeowner, who wanted to remain anonymous, and Hill didn't want to reveal the exact location.
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He said the rare cardinal "behaved totally normal." But, in theory, he said that it could mate with either a female or male cardinal, depending on which of its hormones were active during mating season.
A similar bird recorded by an Erie couple was featured in a National Geographic article in January 2019. That bird, which was red on one side and brown on the other, was spotted and photographed by Jeffrey and Shirley Caldwell.
Daniel Hooper, then a postdoctoral fellow at the Cornell Lab of Ornithology, told National Geographic gynandromorphs are uncommon but not unheard of. He also said they're more likely to be noticed in species where the adult males and females look distinct, such as cardinals.
Hooper told the publication the bird photographed by the Caldwells in 2019 could actually be fertile, since the left side of the bird is female and only the left ovary in birds is functional. That appears to be the case with the bird Hill found, as well.
Gynandromorphism in birds likely occurs when the egg from which the bird developed had two different sex chromosomes instead of just one, according to Natural History magazine.
Hill said he didn't know if the bird he saw was the same one as the Caldwells' but he thinks it's unlikely.
He encouraged other birders to keep "your eyes open for this bird or one like it."
Hill, who was accompanied Saturday by friend Annette Smith, said the Warren County bird, which he photographed from his car while the cardinal was in a pine tree, stood out from a distance even without binoculars.
He said he was "excited to photograph it, to scientifically document it."
Hill, 69, who has been watching birds for 48 years, said he'd never seen one comparable with the bilateral gynandromorph northern cardinal.
"This has been the most exciting," he said.
Contributing: Jay Cannon, USA TODAY
Follow reporter Dana Massing on Twitter @ETNmassing
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This article originally appeared on Erie Times-News: Rare half-male, half-female northern cardinal pictured in Pennsylvania