Its left side [cardinal] is the taupe shade of female cardinals; its right,
the signature scarlet of males. Researchers believe that the cardinal
frequenting the Caldwells’ bird feeder in Erie, Pa., is a rare bilateral
gynandromorph, half male and half female. Not much is known about the
unusual phenomenon, but this sexual split has been reported among birds,
reptiles, butterflies and crustaceans. No one can be sure the bird is a
gynandromorph without analyzing its genes with a blood test or necroscopy,
but the split in plumage down the middle is characteristic of the rare
event, according to Daniel Hooper, an evolutionary biologist at the Cornell
University Lab of Ornithology. He said that gynandromorphs could
theoretically be created through the fusion of two developing embryos that
were separately fertilized. The butterflies are a better example of
gynandromorphism, as they show a variety of mixes of sexual tissue (different
locations and different amounts of tissue). No known human gynandromorphs
have been been observed (yet).
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