Thanks to all who have looked at the bilateral gynandromorph Northern Cardinal in the post below and left comments. It certainly has been an interesting find. It even made the Quad Cities Times!
Birdchick asked the question "Why is this a gynandromorph and not a hermaphrodite?" The answer is that hermaphrodism is a condition where an organism has both male and female reproductive organs but other external characteristics may be normal. In some organisms, hermaphrodism is the normal condition. Gynandromorphism is different. This condition occurs when, in the first mitotic division of an ovum (the division of a fertilized egg from one cell into two cells), the sex chromosomes experience nondisjunction. In other words they do not separate normally and the result is that one of the new cells has chromosomes ZW (the female genotype in birds) and the other cell is ZZ (the male genotype). The result is that the half of the body that develops from one of the cells is female and the one that develops from the other is male. It's even reported that in birds that show sexual dimorphism, the two sides will show differences in size. Is that cool or what?
The other question that people asked was "Could it reproduce?" Well, male birds have paired testes so this bird probably has a testis in it's left side. However, most female birds (there are groups that are exceptions) have only one functioning ovary on the left side of their body. Because this bird is female on the right half I don't know if that would cause it to not have an ovary. Probably the only way to be sure would be by being able to have a peek at the internal organs.
While this phenomenon is rare it has been reported in a variety of bird species including Orchard Oriole, Black-throated Blue Warbler, Evening Grosbeak, American Kestrel and House Sparrow. Apparently nothing is known of the breeding habits of birds with this condition.
I'm hoping to head out tomorrow and do a bit of birding if the weather cooperates. Who knows what new and bizarre things are out there to find?