Penises are weird all across the animal kingdom, but bird penises take the cake for being strange. Male bird reproductive organs have changed vastly over millions of years of evolution, and that kind of development has left some birds with what scientists refer to as “nubs,” and other birds with penises that take up the length of their body.
Do birds have penises? Sort of, yes. It’s not a question that’s as easy to answer as you would think. Some birds in the same family, the ratites for example, have developed penises that are completely different from each other. Some bird penises are uniquely shaped unlike any other bird. Take the duck penis, for example, which resembles a corkscrew. Some don't have penises at all.
Male birds have a unique and varying set of penises, or lack thereof. And while all together strange, male bird reproductive organs are definitely fascinating.
Despite claiming a species that contains one of the largest penis-to-body ratio, most birds don't even have a penis. Out of the 10,000 species of bird, about 3 percent have penises. Some of the types that don't: eagles, flamingos, penguins, and owls. Chickens still have traces of their penises, but what's left of their penises are tiny nubs that can't penetrate anything.
Here's a crazy fact: some birds might be evolving to regrow their genitals. A group of obscure South American galliformes called cracids have penises despite being related to the chicken, which lacks male genitals. Scientists are trying to determine how and why a cracid regrew their penises while chickens don't. It could have something to do with the mechanical makeup of a cracid, but researchers just aren't sure.
Ducks are one of the few types of birds that actually have penises, but it doesn't have the "normal" penis characteristics. Duck genitals are flexible when erect. Rather than becoming hard with blood, a duck's penis is controlled by lymph - a colorless fluid containing white blood cells.
Ducks penises are also often larger than their bodies. The Argentine Lake Duck has the longest bird penis ever - measuring in at 16.73 inches.
Duck penises - and duck vaginas - are shaped like corresponding corkscrews, which isn't exactly an easy fit. For male ducks to successful impregnate female ducks, a female duck has to be a willing participant. If she wants to mate, she will position her body in a way that makes it easier for male ducks to fertilize her eggs.
Ducks are known to be extremely sexually aggressive. Often males force themselves on females, dominating the females physically. In response, female ducks have evolved elaborate reproductive organs which make it hard to inseminate them without consent.
The Argentine Lake Duck is an example of a duck using force to sexually dominate his partner. Males use their penises, often measuring more than 16 inches, to literally lasso and capture female ducks.
Researchers at the University of Alaska theorize that the duck uses its penile advantage to trap escaping females. "Our best guess is that the birds use [the long penis] as a kind of lasso… The males have to chase the females, and even during copulation the females are trying to escape.”