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Half-Male, Half-Female Cardinal Has a Rough Life


Image credit: Peer Lab, Western Illinois University

The picture here shows this cardinal is kind of unusual split-sex gynandromorphy, because on its left side, it owns the bright red male plumage, but on its other half, it has the brownish-gray female plumage.

In reality, we can see some natural gynandromorph ones such as butterflies, lobsters, and chickens. However, scientists have seldom observed them so closely in the wild. Therefore, Brian Peer and his collegue from Western Illinois University were engaged in intensive observation of the bilateral gynandromorph northern cardinal (Cardinalis cardinalis) around bird feeders for nearly forty days starting from December of 2008 to March of 2010 in the northwestern part of Illinois. During such period of time, the researchers had bird never found the bird being paired with another cardinal and neither heard it vocalizing. In addition, they did not find the bird to be prone to “unusual agnostic behaviors” from other cardinals. Such latest findings have been released in the recent edition of the Wilson Journal of Ornithology.

Among most mammals, sex chromosomes, namely XY for males, XX for females, play the decisive role in the formation of either male or female gonads, which then give off hormones in the period of early developmental stages that give direction to the sex of other cells.

As far as birds are concerned, they have a unique ZW sex determination system that is the females being ZW and males having ZZ. So hormones are not so decisive in regard to most mammals. According to the study in 2003 about zebra finches whose brains were almost genetically half male and half female, scientists discovered that the sex differences were neural in origin, and not gonadal. Based on 2010 study targeted on three gynandromorph chickens, that team concluded that the female side was comprised of female cells with female chromosomes, while the male half was mostly made up of normal male cells with male chromosomes. Therefore, it seemed that their cells would follow their own instructions rather than those of the gonads.


Image via Peer Lab

Journal reference: Peer, Brian D., and Robert W. Motz. “Observations of a Bilateral Gynandromorph Northern Cardinal (Cardinalis cardinalis).” The Wilson Journal of Ornithology 126.4 (2014): 778-781.