It鈥檚 a sight to behold: Every spring, male Greater Sage-Grouse gather on a flat patch of sagebrush prairie to 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鈥攄ancing and singing their way to an invitation to mate.
Halfway around the world, Kakapos鈥攆lightless parrots with whiskery sideburns鈥攕pend their nights singing. About the size of a housecat, a male Kakapo鈥檚 whole body pulses with each of white noise. That鈥檚 lekking, too.
And in the lush forests of South America, also lek. But for these tiny black-and-white songbirds, the go-to move is part dance, part drumroll: They snap, crackle, and pop 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 鈥渓eks鈥? It turns out the definition of a lek is hard to pin down. 鈥淚t鈥檚 not as neat and tidy as you might see it in an animal behavior textbook,鈥 says , a biologist at the University of Nebraska鈥揕incoln 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 . 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鈥檚 got 鈥渓unch鈥 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鈥檚 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.
Next, you need your routine. To human eyes, each bird鈥檚 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鈥檚 clear that, if you鈥檙e 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鈥檙e a nocturnal Kakapo or a sage-grouse hitting the leks before dawn, noises take precedence because they echo across the dark countryside. 鈥淚t鈥檚 pretty clear that long-range visual signaling is not really a thing that鈥檚 going on under those conditions,鈥 Gibson says. But if you鈥檙e a Sharp-tailed Grouse lekking after the sun is up, your fluffy white tails, bright purple air sacs, and airplane shuffle dance鈥攚ings 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鈥攏othing else. Some avian mating displays flaunt a male鈥檚 resources, such as for their nest quality, or who exhibit hoarded trinkets. But leks cater to the shallowest of singles, not to gold diggers. That鈥檚 because moms of many lekking species raise their young without any help from dad. As a result, a mate鈥檚 looks and moves matter, but his resources and territory don鈥檛. And so 鈥渓ek鈥 is defined, in part, as a courtship transaction that doesn鈥檛 offer obvious material benefits to females. 鈥淚t鈥檚 a funny way to define a mating system,鈥 Gibson admits.
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鈥檛 part of that definition and, indeed, leks also occur . The casual observer may not spot these leks, since they sometimes rely on scent chemicals, for example, as in . 鈥淭here鈥檚 a concept of having a lek that doesn鈥檛 map onto a particular channel of communication,鈥 Gibson says. These leks are not well understood, given that human senses can鈥檛 reliably track unfamiliar chemical signals.
Dancing birds, on the other hand, are easy to follow through the lekking ritual itself: They鈥檙e large and use sensory signals that humans know well. But that鈥檚 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鈥檛 follow individual birds and their reproductive success. As a result, they don鈥檛 know which traits attract females to mate with one male over another, or how leks shape populations. Until then, we鈥檙e left with the drama of the ritual itself to understand how a male gets lekky鈥攅rm, lucky鈥攚ith the ladies.