Greater Sage-Grouse parade their plumage and booming air sacs on a lek. Video: K. Theule/USFWS/Flickr CC (BY 2.0)

Science

What the Heck Is a Lek? The Quirkiest Mating Party on Earth

Consider this your guide to the mating ritual that shapes the lives of a hundred dancing, singing bird species.

It’s a sight to behold: Every spring, male Greater Sage-Grouse gather on a flat patch of sagebrush prairie to put on a show for local females before a backdrop of snow-capped mountains. In a group, they parade their snowy ruffs and pointy tail-feathers, and as they do the greenish-yellow air sacs on their chests thump in rhythm to produce a twanging glug. The sights and sounds carry well across the prairie, and successfully draw in female grouse roaming the countryside.

The males are lekking—dancing and singing their way to an invitation to mate.

Halfway around the world, Kakapos—flightless parrots with whiskery sideburns—spend their nights singing. About the size of a housecat, a male Kakapo’s whole body pulses with each tuneless boom of white noise. That’s lekking, too.

And in the lush forests of South America, White-bearded Manakins also lek. But for these tiny black-and-white songbirds, the go-to move is part dance, part drumroll: They snap, crackle, and pop special feathers on their wings to call females to a cleared forest courtyard.

Mating often brings out the weirdest side of nature, but why have certain birds developed such diverse rituals, and what makes them considered “leks”? It turns out the definition of a lek is hard to pin down. “It’s not as neat and tidy as you might see it in an animal behavior textbook,” says Robert Gibson, a biologist at the University of Nebraska–Lincoln who has studied leks in American prairie species. But there are three key ingredients in any lek.

First, you need a bunch of birds. Typically, males gather to put on an impressive show to attract a mate, and females wander by to check out their options. It might seem unwise for second-rate dancers to expose themselves to that kind of judgement and competition, but assembling in large groups offers two benefits. Just like at a nightclub, males convene at a lek so females know where to find them. And the gritty reality is that males lek for safety. Take those sage-grouse, which make tasty treats for Golden Eagles. If one grouse dances alone in the open, he’s got “lunch” written all over him; if there are twenty, each bird has better odds of making it out alive.

Once a group is assembled, some species carefully choose a natural stage for their lekking ritual, although it’s not a universal requirement. A lekking stage could be a dip in the earth that amplifies sounds like an amphitheater. Sometimes, a bird will put in the work to clear leaves from a patch of ground to let his dance moves shine.

When they're feeling lekky, White-bearded Manakins gather in groups to snap, crackle, and pop their feathers. Photo: National Geographic Creative/Alamy

Next, you need your routine. To human eyes, each bird’s moves look pretty much the same. But the responses from their intended audience range from an icy-cold shoulder to a mating invitation. So it’s clear that, if you’re a bird, you can tell that some lekkers are better made for the spotlight than others.

Lekking can involve noise, movement, or both. If you’re a nocturnal Kakapo or a sage-grouse hitting the leks before dawn, noises take precedence because they echo across the dark countryside. “It’s pretty clear that long-range visual signaling is not really a thing that’s going on under those conditions,” Gibson says. But if you’re a Sharp-tailed Grouse lekking after the sun is up, you’d be a fool not to show off your fluffy white tails, bright purple air sacs, and airplane shuffle dance—wings outstretched, head down, now move those feet!

Finally, to earn the title of lek, the show must sell only an individual bird and his genes—nothing else. Some avian mating displays flaunt a male’s resources, such as House Wrens choosing mates for their nest quality, or male Satin Bowerbirds who exhibit hoarded trinkets. But leks cater to the shallowest of singles, not to gold diggers. That’s because moms of many lekking species raise their young without any help from dad. As a result, a mate’s looks and moves matter, but his resources and territory don’t. And so “lek” is defined, in part, as a courtship transaction that doesn’t offer obvious material benefits to females. “It’s a funny way to define a mating system,” Gibson admits.

Sharp-tailed Grouse. Photo: Rick Bohn/USFWS/Flickr CC (BY 2.0)

So, back to our main question: What the heck is a lek? In summary, it's a gathering of males to show off their genes without any material benefits to a female. You might notice that birds aren’t part of that definition and, indeed, leks also occur among fish, insects, and even some mammals. The casual observer may not spot these leks, since they sometimes rely on scent chemicals, for example, as in some species of fly. “There’s a concept of having a lek that doesn’t map onto a particular channel of communication,” Gibson says. These leks are not well understood, given that human senses can’t reliably track unfamiliar chemical signals.

Dancing birds, on the other hand, are easy to follow through the lekking ritual itself: They’re large and use sensory signals that humans know well. But that’s where most of our understanding about lekking ends. During the rest of the year, many lekking species are difficult to track, which means scientists can’t follow individual birds and their reproductive success. As a result, they don’t know which traits attract females to mate with one male over another, or how leks shape populations. Until then, we’re left with the drama of the ritual itself to understand how a male gets lekky—erm, lucky—with the ladies.

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