The extraordinary sex life of the common mallard

The mallard seems like such an innocent little duck.

We see them paddling along ponds in the afternoon, green heads bobbing, orange feet flashing beneath the waves, itty bitty fuzzy ducklings in tow, quacking away, perhaps tipping their beaks to passers-by or gobbling up bits of bread from generous octogenarians – the very picture of incorruptible, pure cuteness.

Yet they've also got a sex life that would make even the most carnal Casanova blush, full of gang rapes and remarkably complex genitalia.

"Mallards are interesting in that they have external penises," notes Lee Foote, a University of Alberta biologist who has studied, shot and eaten many a mallard over the years.

Whereas most birds don't have penises at all (just a sensory spot known as the cloaca), the mallard has one that sticks out many centimetres during copulation.

The mallard penis and vagina also both have a complex, corkscrew-like shape that locks mates together during copulation, notes Pat Kehoe, a St. Albert resident and biologist with Ducks Unlimited.

"It's amazing, the length, too," he said.

For those of you that are still reading, the mallard is likely the most common and most recognized duck in North America. Males are hard to miss with their chestnut chests, white-grey bodies, curly black tails, yellow bills, white collars and iridescent emerald heads. Females are mottled brown with orange bills.

The females look a lot like gadwalls, while the males resemble northern shovelers, Foote and Kehoe say.

The best way to tell them apart is to check out the wing. Mallards will have a blue patch with white borders on their wings called the speculum that's unique to them.

Foote describes the mallard as "the Chevy Impala of ducks" – omnipresent and super-adaptable. They'll nest pretty much anywhere and eat pretty much anything – even food right from your hand.

Mallards should be arriving in force this Easter weekend as they fly up from Calgary and the U.S., Foote says. If you hang out in a corn or wheat field, you may even see a duck-vortex form as swarms of migrating mallards spiral out of the sky for a snack.

"It's really spectacular," Foote said.

Once here, expect these ducks to immediately pair off in preparation for nesting, Kehoe says.

Unlike most waterfowl, mallards prefer to nest upland, often marching their ducklings up to a mile to get to the nearest pond. Expect mallard nests to show up in schoolyards, downtowns and other nonsensical spots as a result.

Mallards look for "undisturbed" locations free from predators when they nest, Kehoe explains. Since humans usually aren't a threat – this reporter has had one yawn at him while he was a metre away – mallards have no qualms setting up shop in your yard.

Really wild sex lives

A mating male will generally follow his mate of choice, wooing her by bobbing his head, dipping his beak in the water and letting water drip off, and showing off his green plumage.

Mating involves the male climbing onto the female and shooting out his penis with surprising speed – it reaches its full length in less than a second. The male often grips the female's neck with its beak to hang on while this happens, Foote notes – some females go bald on the back of their necks as a result.

While theoretically monogamous, mallards will often engage in what used to be called "rape chases," but are now known as "forced copulations." This involves several males chasing a female and then forcefully mating with her – an act that can result in the female's death.

"I've seen cases where six or eight males will be chasing a female in flight," Kehoe says. "It's a very violent situation."

Bizarrely, Foote notes, the females actually elicit this behaviour by intentionally flying over the territory of other males. Evolutionary biologists believe that female mallards encourage these forced copulations to raise the odds of successful fertilization.

"If you only get to mate once or twice in your life, you want to make sure you get with a male who isn't shooting blanks," he says.

The bizarre genitalia of the mallard likely evolved as a defence to this forced mating, Kehoe says.

Research by Patricia Brennan, an evolutionary biologist at the University of Massachusetts Amherst and one of the few experts on duck genital morphology in the world, suggests that the female can use the many twists and turns of her vagina to slow the progress of the penis, letting her influence which males get to fertilize her eggs. (Males evolved equally corkscrewed genitals as a countermeasure.)

The rest of the year

Kehoe says male mallards ditch their partners after mating and head north around June to moult and grow new flight feathers for the fall. They become flightless for about two weeks in the process, but also ditch their flashy colours for the great camouflage of the female mallard.

The females stick around to protect their ducklings, which quickly learn to feed themselves. This often involves marching the babies to the nearest waterway, braving traffic and sewer grates in the process. The babies gain their flight feathers around July, with about six out of 10 surviving to this point.

This reproductive success means that mallards can be hunted extensively without risk of population collapse, Kehoe says. Still, they need wetlands to survive, which is why groups such as his work to preserve them.