Rare part-male, part-female songbird found in Pennsylvania

Genetically, gynandromorphs are part male and part female and in this rare songbird, its unusual gender line runs right down the middle.

Scientists in Pennsylvania said they have caught and banded Rose-breasted Grosbeak gynandromorph that has its male characteristics on its right side and the female ones on the left.

“The entire banding team was very excited to see such a rarity up close, and are riding the high of this once-in-a-lifetime experience,” said Annie Lindsay, bird banding program manager at the Powdermill Nature Reserve at the Carnegie Museum of Natural History in Rector, PA.

“One of them described it as ‘seeing a unicorn’ and another described the adrenaline rush of seeing something so remarkable,” Lindsay added.

Rose-breasted Grosbeak gynandromorph. Photo: Annie Lindsay/Carnegie

The bird was located on Sept. 24.
Rose-breasted Grosbeaks are sexually dimorphic, which means males and females have different plumage pigmentations.

This particular bird has the male pink “wing pits,” breast spot, and black wing feathers on the right side. Meanwhile, the female yellow wing pits and browner wing are on the left side.

So, can it breed?

Researchers said since usually only the left ovary is functional in birds, and the left side of this bird is the female side, this bird could theoretically produce young.

But to do that, it needs to attract a male.

However, its ability to reproduce could also depend on whether it sings like a male. If it does, scientists said, it could attract females and a territorial response from other males.

Powdermill’s Avian Research Center has been banding birds for 64 years and in that time, has recorded fewer than 10 bilateral gynandromorphs.

So this really is a big deal for the banding team.

“They all are incredibly grateful to be part of such a noteworthy and interesting banding record,” Lindsay explained. “Bilateral gynandromorphism, while very uncommon, is normal and provides an excellent example of a fascinating genetic process that few people ever encounter.”


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