BirdNote; A Cardinal That's Half Male, Half Female

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A Cardinal That’s Half Male and Half Female

Written by Bob Sundstrom

This is BirdNote.

[Northern Cardinal song, https://macaulaylibrary.org/asset/49062 .05-.09 here and there]

In nature, things aren’t always black or white, male or female. There have been sightings of cardinals that are red on one side and brown on the other, indicating a bird that is half male and half female. This anomaly occurs in other species of birds, as well, not just cardinals.

Scientists call these birds bilateral gynandromorphs, (pron. ji-NAN-druh-morf), known informally as “halfsiders.”

Birds’ sex chromosomes are different from those of mammals. Male mammals have one of each sex chromosome, an X and a Y. Female mammals have two X chromosomes. But in birds, this is reversed. The female has two different sex chromosomes, while the male has two of the same.

So, if a bird’s egg develops with two intact nuclei, this second nucleus can also be fertilized. It’s sort of like when you get a chicken egg with two yolks. But in this case, it’s like the yolks have fused. And the result of these fused embryos is a chick that’s half male and half female — just like that half-red and half-brown cardinal. As far as we know, halfsiders do not reproduce.

Check out a photo of a halfsider cardinal on our website, BirdNote.org.

For BirdNote, I’m Mary McCann.

Today’s show brought to you by the Bobolink Foundation.

[Northern Cardinal song, https://macaulaylibrary.org/asset/49062 .05-.09]

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Producer: John Kessler

Executive Producer: Sallie Bodie

Editor: Ashley Ahearn

Associate Producer: Ellen Blackstone

Assistant Producer: Mark Bramhill

Bird sounds provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York. Recorded by

BirdNote’s theme was composed and played by Nancy Rumbel and John Kessler.

© 2020 BirdNote April 2020 Narrator: Mary McCann

ID# gynandromorph-01-2020-04-07 gynandromorph-01