Mallards ducks (Anas platyrhynchos) excel at coexisting with us, so sighting them in urban areas or elsewhere is often a dull encounter, until they do something remarkable that changes your opinion of them—forever.

Put a lone male together with a mating pair and you may witness a chaotic aerial chase followed by an odd threesome forced on the female. Apologies for the poor image quality (due to fast motion and the birds moving towards or away from me), but you get the idea.

This is the beginning of the first chase of the poor female duck. Credit: Yalakom

Credit: Yalakom

Here you can really see the female trying to escape. Credit: Yalakom

The odd threesome… Credit: Yalakom

The male on the right is trying hard to push the other away, only I’m not sure which one is the original female’s partner. Credit: Yalakom

The female finally got out… Credit: Yalakom

…and the two males remained in the most awkward position for a few seconds. Credit: Yalakom

Soon enough, they stood up and went on with chasing the female. Credit: Yalakom

The helpless female seems to be running for her life! Credit: Yalakom

Credit: Yalakom

Credit: Yalakom

One male tripped, too much excitement… Credit: Yalakom

Taking a deep breath… Credit: Yalakom

…and on again. Credit: Yalakom

Credit: Yalakom

There is no escape. Credit: Yalakom

Credit: Yalakom

Finally, the intruder gave up, but only for a little while. Credit: Yalakom

The tumultuous chase repeated several times, though only once did the lone duck manage to get to the female.

This is not unusual duck behavior, on the contrary. Forced copulation in mallards is so common that a term was coined for it, i.e. “intent-rape flight” or “attempted rape flight”. The expression describes the occurrence of lone males (who fail to pair off with a female during breeding season, that is right now) flocking together to pursue a female until exhaustion and subsequently mate with her in turn. The female I photographed was “lucky” that only one male attempted to cover her.

In response to such violent, sometimes deadly sexual assaults, females have evolved sophisticated genitals that allow them to choose their mating partner—in most cases. To match this complexity of structures, males have similarly developed more elaborate phalluses (not a common organ in birds, 97% don’t have one), an outstanding example of co-evolution.

In the end, what is at stake in this seemingly endless evolutionary “arms race”, as biologists call it, is who gets to control reproduction, hence paternity. Female mallards obviously take the issue very seriously and seem to be winning the battle given that only 3% of ducklings are the result of unwanted intercourse, which can represent up to one third of all matings.

That’s another chase that took place a few minutes later. The female managed to escape with her mate. Credit: Yalakom

Credit: Yalakom

Credit: Yalakom

Credit: Yalakom

Location: Botanical Garden, Rostock, Germany

REFERENCES – Coevolution of Male and Female Genital Morphology in Waterfowl (research paper), Brennan et al., Plos One, May 02, 2007. In Ducks, War of the Sexes Plays Out in the Evolution of Genitalia, by Carl Zimmer, New York Times, May 1, 2007. Ducks Wage Genital Warfare, by Charles Q. Choi, Live Science, January 11, 2008. Ballistic penises and corkscrew vaginas – the sexual battles of ducks, by Ed Young, Science Blogs, December 22, 2009