That's one wierd-looking chicken! - Bilateral gynandromorphism

In birds there is a rare mutation that creates a sexual chimera. Birds have a different system to our XY sex-determining chromosome system and this allows the above to happen. In the picture above, the right side is the female side (hen), and the left side is male (cockrel) - so you have a 50/50 male/female split. Isn't it amazing how it's split down the middle exactly!? More about this here.