Twisted Love: Sex Lives of the Duck and Goose

Twisted Love: Sex Lives of the Duck and Goose

Reading Time: 6 minutes

Kenny Coogan THOSE WHO HAVE RAISED ducks for as long as I have will have certainly noticed the fusilli-shaped penis that hangs out of the drake after coitus. But have you ever thought “Why is it that shape?” And no, you don’t have to be a voyeur to be curious about duck sex and keep reading.

After I graduated with a BS in Animal Behavior, I worked at the local aquarium. For Valentine’s Day, I gave a presentation perfectly entitled
“Penguin Romance: Love on the Rocks.” The sold-out (adult-only) crowd was interested in the sex lives of penguins! I discussed penguins that were in same-sex relationships and penguins that reared chicks together for years who later divorced and found new mates. I also talked about the oldest penguin William, a 30-year-old-plus penguin, who was in a permanent molting state, blind, and had two separate nests, each with their own mistress. As I gave that presentation, I thought how similar our domestic poultry behave to these penguins. Fast forward about 15 years and New York Times-bestselling author, Eliot Schrefer, publishes Queer Ducks (and Other Animals): The Natural World of Animal Sexuality (Harper Collins, May 2022). In it, he discusses sexual behavior in the natural world, from fish to bonobos, from bulls to ducks and geese.

Duck sex
Cover of Schrefer’s book. Used with permission of Eliot Schrefer

After writing a Washington Post piece based on the research from Queer
, Schrefer noticed that, “Half of the comments were from farmers who
said, ‘Well duh, we’ve been seeing this since we’ve been farming. Come visit my chickens, my pigs, my cows.’ I think the research is most surprising for people who don’t live around either wild animals or livestock.”

In the duck and geese chapter, Schrefer mostly talks about three-bird nests. “Sometimes, it is female-female-male but most often, it is male-male-female, which happens between 3 to 6% in ducks,” Schrefer says. “The interesting part to me is that there is a higher percentage of survivorship in nestlings because they have three parents. Of the parenting strategies, aquatic birds have a tough time, since their nests are on the ground. If a predator comes, they can’t leave the nest because that is it for chicks.”

Jules Zuckerberg cartoon. Used with permission of Eliot Schrefer.

He explains that it’s an evolutionary benefit to have one extra defender.
What else is surprising is that three-bird nests are often seen on the outside of colonies. “It may be a group selection on the evolutionary level to have these boisterous and vigilant defenders on the outside where predators are more likely to come,” Schrefer explains.

The Corkscrew

To learn why ducks have a corkscrew penis, I interviewed Dr. Patricia
Brennan who studied that exact topic for her postdoctoral work. She went to a Pekin duck farm to learn more. “When I dissected them, I was really blown away on how large the penises were for their body size and how they look like tentacles, and they are all white and weird,” Brennan recalls.

duck sex
Convulted vagina and long penis from a wild mallard. Photo by Dr. Patricia Brennan.
Simple vagina and short penis from an African goose. Photo by Dr. Patricia Brennan.

She thought the female ducks had to have something different. She went back to the farmer and got a few females to dissect and what she saw really surprised her. Brennan thought she was going to find a large vaginal sac, but instead she found that they have really convoluted vaginas, with blind pouches at the entrance and then a series of spirals as it approaches the shell gland. “And those spirals spiral in the opposite direction of the penis. Which made absolutely no sense. As I started learning more about duck behavior, I found that there is a lot of sexual conflict. A lot of the copulations are forced copulations,” Brennan says.

She went into the field and collected 16 duck species and the domesticated African geese who have varying degrees of forced copulation. Species that had the most have really twisted vaginas and penises, and species that had more consensual sex had simple penises and vaginas.

“It looks like there is an evolutionary arms race in ducks — literally — over the control of reproduction,” Brennan explains. “This is why breeders know to keep a high ratio of males to females because if you keep a lot of males, they are not only going to beat each other up but also the females. While you can’t breed for ‘niceness,’ you can follow nature and do what they already do — reduce competition.”

Pair Bonding

Brennan says that waterfowl are so cool because they form pair bonds. Mallards and most other duck species form at least temporary pair bonds
during the mating season. Females do the incubation on their own and are
often killed at the nest. And that causes more males in the population. “When they pair up, there are extra males. So, they fly around and look for females who are already paired up with a male and force them to copulate.

This is not good for the female because they have already made their choice.” She explains that the complex vagina limits the fertilization of these aggressive unwanted males. “The reason why this behavior doesn’t disappear is that males that are paired up also force copulation. This strategy persists because a little bit of paternity is better than zero paternity, evolutionarily speaking, especially in a year where they can’t
secure a mate.”

People have been raising (and eating and therefore dissecting) poultry for
thousands of years. I asked if she was the first person to notice these complex sexual organs. “I am the first person to publish it, but I can’t imagine that nobody has ever seen it before because it is pretty obvious. One of the people we first contacted is a guy who specializes in fertility in ducks and has looked at duck vaginas for a very long time. But he was looking at a specific area called the utero-vaginal junction where the sperm storage tubules are,” Brennan recalls.

She says he would dissect vaginas by just cutting to the section that answered his questions. “So when we sent him our photos he almost fell out of his chair because he was like ‘Oh my gosh, there they are! I have never seen them.’ But that’s okay because as scientists we all ask different questions.” In Queer Ducks, Schrefer writes about male pairs of mute swans who spend their entire lives together but will invite a female in for the breeding season. He also talks about the Greylag goose triumph ceremony.

Greylag geese. Photo by Kenny Coogan.

“A male will go pick a fight with another male to only return as the victor to his mate to convey the message ‘Hey look what I did for you baby,’” Schrefer says.

Three-Bird Nests

“I love that when you have three-bird nests, it’s not just cohabitation
or survival strategy. When the male returns from the triumph ceremony they are equally as likely to do it to their male partner as they are to their female partner. That is the proof of the union to ornithologists.”

Schrefer adds that we have a way too narrow view of what sex is in the
non-human world. “For too long, we have looked at animal sex as procreation only and anything else as a strange deviation to that. Now we have come to see the massive benefits that the diversity of sexual expression. Outside of male-female sexuality there is a wide range of adaptive and evolutionary strategy to them.”

“Just because we don’t want to talk about vaginas and penises doesn’t
mean they aren’t important,” Brennan says. “They are critically important
for reproductive success, evolutionary success, and health. There is no reason why we shouldn’t be studying them and the only reason why we don’t is that some people are embarrassed by them. We’re innately interested in sex and there is a lot to be learned.”

KENNY COOGAN is a food, farm, and flower national columnist. He has a master’s degree in Global Sustainability and leads workshops about owning chickens, vegetable gardening, animal training, and corporate team building. His upcoming book, Florida’s Carnivorous Plants, will be published in July 2022 and will be available at

Originally Published in the February/March 2023 issue of Backyard Poultry and regularly vetted for accuracy.

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