These pictures look like something out of Star Trek. I was not aware
that there were creatures in the world that were literally female on
the left side and male on the right side.
I certainly never heard of this either.
When I first saw the article, which mentioned that this phenomenon
is noted in only a few species, I thought... ah, instead of these birds
using the XY system of sex selection, like we do, perhaps they're an
XO species - so during the initial cell division, one of the X chromosomes
got lost, creating a half-male half-female bird.
But it turns out this is not the case. Instead, cardinals belong to the ZW
sex selection system. In that one, a male is ZZ, and a female is ZW; the
Z chromosome is big and rich with genes, like an X chromosome, and
the W is just a stub, like a Y chromosome.
So their sex selection is exactly like ours, except that the resultant sex
of the individual is the opposite. Thus, I am at a loss as to why
gynandromorphy is possible in cardinals and not in humans and creatures
like them (other forms of hermaphroditism are possible in humans, but
not that one).