I’ve been scarred. Really. Read on. I promise that I will not scar you unless you want to be scarred. It has to do with bird sex, so first we must discuss the way most birds have sex before getting to the way that one bird in particular has sex.

All birds have this thing called a cloaca from which they expel both urine and feces. This is true of all amphibians and reptiles and even some mammals as well. I’ve never really understood why we humans (and the vast majority of other mammals) have separate systems, and I’m not going to look it up now. I have important bird business to discuss.

Okay, so all birds have these things. Most birds also use the cloaca for sex, “This means that the same opening that excretes feces and urine is where eggs are laid.” So in Chicken Run when the two rats, Nick and Fetcher, refer to eggs coming out of chickens “bums” they are exactly right. (This is, by the way, the best way to learn biology: from animated features.) In case you are wondering, this is not the scarring part of the story — not even close.

The way that most birds mate is kind of cool. When they are ready for sex, their cloacae puff up. So the male balances on the back of the female. She splits her back feathers to allow access to her cloaca. He maneuvers his body so that their cloacae can touch — this is called a “cloacal kiss.” It only lasts a second or so, but that’s enough time for the seamen to get transferred. This makes sense. Imagine if humans had to copulate standing up in a hammock and you get the idea.

It seems like such a charming way to have sex. There is something kind of brutal about the whole penis and vagina arrangement. On the other hand, having a single orifice where urine, feces, and babies come out strikes me as kind of disgusting. I’m already freaked out enough that the urine and baby place is the same. Obviously, baby birds have the advantage that they come out in neat little packages.

Okay, so that’s how most birds have sex — like those pretty gulls above. But as I said, not all. In particular, the mallards have penises and vaginas. And they generally have the kind of sex lives that most animals have. The male and the female link up, have some sex, have some babies, and the guy goes on his merry. But the males who do not manage to find a mate will go after lone females and beat them up and turn them into a kind of sex slave. Of course, dolphins do the same thing. But you need to remember that this is not what scarred me. Humans partake of sex slavery, and that oh so holy Bible that people like to talk about being the source of all morality is absolutely fine with it.

What is scarring is the mallard penis. Mallard penises can be over a foot long. That’s about as long as the duck is itself. And it is corkscrew shaped. You can read all about it along with information about duck and sea otter necrophilia in a Dylan Matthews article, Seven Adorable Animals That Are Also Murderous Monsters. But be aware that if you click over, you will be treated to a duck penis becoming erect in slow motion. And once seen, it cannot be unseen.