PENNSYLVANIA (NEXSTAR/WGN) — A longtime birdwatcher in Pennsylvania had what he called a “once-in-a-lifetime” bird sighting — a rare cardinal that appeared to be half male and half female.

“I had a once-in-a-lifetime, one in a million bird encounter!” said James Hill, who described the bird, known as a bilateral gynandromorph northern cardinal, as “a bird divided right down the middle, half male and half female.”

Typically, male cardinals have bright red plumage, while females are “buffy brownish,” Hill said in a Facebook post. This bird was half and half.

Hill, who spotted the cardinal Saturday, said the bird was female on its left side and male on its right and could in theory mate with a male bird and lay eggs or mate with a female and father the eggs.

Hill, who’s been birding for 48 years, heard about the bird from a friend of the homeowner where the bird was spotted.

“This really piqued my interest since I wasn’t sure if she was referring to a hybrid, or a much rarer gynandromorphic bird (a bird that is ½ male and ½ female),” Hill said.

He got the homeowner’s permission to snap pictures of it.

Hill, citing National Geographic and Daniel Hooper, a postdoctoral fellow at the Cornell Lab of Ornithology in 2019, said gynandromorphs, called “half-siders,” are rare but known.

“They likely occur across all species of birds,” Hooper told National Geographic, “but we’re only likely to notice them in species where the adult males and females look distinct from each other.”