How cool is this? This cardinal is a gynandromorph, where an animal is actually split – usually along a midline – and expresses sex characteristics of a male on one side & of a female on the other.
So to get gynandromorphs in flies, all that has to happen is that one X chromosome gets lost in one cell when the initial cell in a female (XX) zygotes divides in two. One half of the fly then becomes XX, the other XO, and the fly is split neatly down the middle, looking like the one below. But gynandromorphs don’t have to be “half and halfs”. X chromosomes can get lost at almost any stage at development, so flies can be a quarter male, have irregular patches of maleness, have just a few male cells, or even a male patch as small as a single bristle.
I’m not sure what the genetic similarity is between these birds and people who are intersex at birth, but some smart biogeneticist out there will let me know.