Every year people decide that it is just too cute to keep the ducks and the chickens together, including the drake. And every year someone is broken hearted because a poor biddy died in agony after a drake attempted to mate with her. Here are the basics: Chickens do not have a penis; they perform what is known as the cloacal kiss in order to mate. Ducks have penises; some ducks have very large genitalia. Researchers have found that the more prone a waterfowl species is to forced copulation, the larger the penis. Google the subject for more information. In short, the drake has a very rapid, high-powered erection and a corkscrew member; the female has a reverse corkscrew orifice, complete with blind pouches to misdirect a male who is forcing her to mate with him; these defenses meant that 3% or fewer water fowl eggs are fertilized by forced copulation. When she wishes to mate, she simply relaxes, and things go into the right places; if she is tense and struggling, her natural defenses make successful fertilization very tricky. Biddy doesn't have these defenses, and her body is not evolved to accommodate a large male member. Biddy can be ruptured internally by a randy drake, and can die in horrible pain from a slow infection. Biddy suffers far more than a broken heart in these situations.