Being Half Girl, Half Boy

A flash of red in the gloom of a snowy winter day. A red bird sits on the bird-feeder. Only it’s not only red, it’s also brown. Sitting on the tree branch of a house in Rock Island, Illinois, this bird has male plumage and female plumage. This photograph has scientists scratching their chins and doing some serious research.

This northern cardinal really does have one side of its body that has the plumage of a male cardinal (red) and the other side with female plumage (light brown). This woman looking out her window was surprised and confused by the image sitting before her.

These weird birds are sometimes seen, but rarely. Brian Peer, a Professor of Ecology and Curator of Birds and Mammals at Western Illinois University, and Robert Motz, share their long-term observations of a free-living “halfsider” Northern cardinal, that they made during 40 consecutive days. Their extensive research shows that these birds never paired with other cardinals. Research also showed that it never sang, and when pre-recorded songs of northern cardinals were played, it didn’t act aggressively the way a normal bird would do. This seemed to be a solitary bird, keeping to itself, but no other birds ever acted aggressively to it. which surprised scientists.

Unfortunately, this bird was never captured to be tested. But previously published research on halfsider chickens found mostly male cells in the side with male plumage and mostly female cells in the side with female plumage. The theory about how these birds came to be mostly revolve around eggs. Some scientists think that these were originally two separate eggs that then fused inside of the mother’s embryo.

In halfsider birds, cells on each side of the fused embryo develop based on their chromosomal makeup, regardless of the hormonal milieu. But human embryos develop based upon the hormonal milieu that their cells are exposed to, regardless of their chromosomal makeup. For this reason, gynandromorphism doesn’t occur in humans or other mammals. In addition to birds, halfsiders sometimes pop up in a variety of spineless creatures (crustaceans, arachnids, and insects).

The questions about this mutated bird continue to pile up, baffling scientists. These findings create an interesting and weird scientific study.