Displaying together, is it a win?
The ruff is a wader species with an enormous distribution range, covering almost the entire east-west axis of Eurasia, mostly above 60° north. In Belgium and the Netherlands, this species is virtually extinct as a breeding bird due to factors that today also drive other meadow bird populations toward extinction, mostly related to the intensification of agricultural practices. In Scandinavia and Eastern Europe, the ruff is locally still relatively common, though populations are decreasing here too. In Scandinavia, you have populations in the tundra in the north and coastal meadows or agricultural fields in the south. South of Oulu, research on ruffs in coastal grasslands has been conducted since 2016 by the University of Oulu (Kari Koivula & Veli-Matti Pakanen) and the Max Planck Institute for Biological Intelligence (Clemens Kuepper & Krisztina Kupán).
Beloved ruff habitat!
Ruffs return to the coastal grasslands in early May, when the snow finally melts and the ground is no longer frozen. Males return earlier than females, and this is no coincidence. Male ruffs gather in places with high visibility in the landscape, such as small hills or areas with shorter vegetation. These podiums are better known as leks. This lek behaviour is rare and mainly known from gallinaceous birds, such as the black grouse or the capercaillie. We can also find lek behaviour within other species groups. The well-known cod and the common fruit fly are well-known cases.
And... action! A newly arrived female (out of focus in the center of the frame) caused quite a stir among the males present.
Relatively little is known about lekking behavior. First, there is no consensus yet on the origins of this behavior. While it may seem fun - with males displaying together to attract females - this behaviour has serious implications for the participating males.
The main consequence is that mating opportunities are monopolized by just a few males, and sometimes even by a single individual: the alpha male. Furthermore, males have to invest a great deal of energy in this. They need to look attractive and must try to defend a territory on the "stage". Fights are not uncommon.
On the other hand, there is a major advantage for females: they need to invest less time in searching for a suitable mate. Presumably, the leks also serve as indicators of suitable nesting habitat, thus providing new females in the population with a clue as to the best places to build their nests.
A disadvantage for the females is that the males do not help incubate the eggs and raise the chicks. In short, lekking behavior fascinates behavioral and evolutionary biologists — and ruffs add an especially intriguing twist.
A disadvantage for the females is that the males do not help incubate the eggs and raise the chicks. In short, lekking behavior fascinates behavioral and evolutionary biologists — and ruffs add an especially intriguing twist.
Fights over territory or attention to a female are not uncommon. Only dominant males engage in such fights. Satellite males (see bird on the right) remain aloof.
Brains over brawn
Ruffs are truly unique because of the existence of alternative reproductive strategies, characterized by three types of males*, each with distinctive plumage and behavior. First, there are the dominant males. These are the most aggressive and often have a fixed location on the lek.
Then there are the satellite males, recognizable by their white collars. Satellite males are less aggressive and try to gain access to females by cooperating with a dominant male. When the dominant male isn't paying attention, the satellite male can take advantage of the situation: pass on his genes to the next generation.
Finally, and very rare (less than 1% of the population), there are the faeder males. These are males that look like females and try to fool the dominant and satellite males to gain access to a female without fighting. Faeders are the embodiment of the saying: "Brains over brawn."
* There are also three types of females, which are morphologically much less obvious.
The textbook example of a satellite man. They don't get any whiter than this!
Classic dominant male. Dark-colored collar, strikingly colored face, and ready to defend his territory!
Feaders look almost exactly like females (slightly larger). Behavior and especially DNA can provide clarity. In this case, the photo shows a female.
How did it get this far? The explanation behind this remarkable phenomenon lies mainly in genetics. 3.8 million years ago, an inversion* occurred within the gene responsible for the hormone balance of birds. This created two versions, the dominant males and the feaders. About 70,000 years ago, another recombination occurred within this supergene, which resulted in the satellite morph. These exceptional events have led to the emergence of three types of males driven by differential hormone production, each with its own character traits. Fascinating, isn't it? I'm not going to explain the entire hormone story. Not everything is known about it yet, but this paper does give a glimpse of what's to come. One last fun fact to conclude is that the sneaky feader males have the largest sperm reserve. The chances of mating are slim, but if they do, they do it well!
Let's spy!
A large part of my fieldwork consists of observing displaying ruffs. I carefully count the number of males present, record their morphs, and keep track of female visits to the lek and whether mating occurs. We also try to capture birds so we can ring and radio-tag them. This provides valuable information about how the birds use the landscape.
Each day begins at three in the morning. After two cups of coffee and a banana, we drive to the grassland where we conduct behavioral observations. Around seven o'clock, we're back in the car; we use the rest of the morning to catch up on sleep. Sometimes we return in the evening, though lek activity is lower. One thing is certain: there's no natural rhythm here. But you won't hear me complaining — this is nature and ornithology par excellence!
I was fortunate — and obliged — to photograph and film during the behavioral observations. In 2025, I spent several nights in the hide documenting their behavior. I'll show you, step by step, what the ruff's courtship display entails.
The ruffs are observed from a safe distance for at least an hour.
When the males are captured, we take various measurements and a blood sample for DNA analysis. The birds are also fitted with radio tags so we can track their movements.
The tag. Birds sometimes lose their transmitters after a few weeks or during migration.
It has its charms, working all night and then getting birds out of the nets at first light.
Start to lek
Around three o'clock in the morning, the first birds are already courting, about fifteen meters from my hide. The first step is to attract females to the lek. When males see females flying overhead, they jump up briefly and flap their wings. With this apparent enthusiasm, they hope to convince the females to visit the lek. Then the real work can begin!
Once a female lands on the lek, it's chaos all over the place. Dominant males may fight each other, while satellite males may try to cooperate with a dominant male—a behavior called codisplaying. This can be beneficial for both males, although dominant males have more successful copulations when no satellite is present (since satellites can disturb possible copulations). Codisplay is making the best of an unfavorable situation.
The interaction between two males can attract a female, allowing the dominant male to mate. However, the satellite male may benefit from the female's proximity when the dominant male is engaged in another fight and ignores the female for a second.
To display their dominance over satellite males, dominant males sometimes place their beaks on top of the satellite male's head—a bit like medieval knighting—or they repeatedly "prod" the other male.
The presence of females always brings ambiance to the lek!
A beautiful example of co-display.
A crucial part of courtship is when the male kneels before the female.
In some rare occasions, satellite males are successful and can mate with a female. This rare occasion is visible in the next video. Pay also attention to the behaviour of the dominant male before and after the satellite male copulated with the female. Somebody is not happy....
A male's ultimate goal is to pass on his genes to the next generation. If the male holds the top spot on the lek, that's usually fine: most of the matings go to a single male.
Males try to convince females by kneeling, raising their ruffs, and extending their wings. Females, in turn, can show interest by slightly opening their wings. When a female crouches down, the message is clear: she's ready to mate.
From that moment on, the male's job with that female is done. After all, he's not busy incubating the eggs or raising the chicks. It's much better to mate a few more times and thus produce even more offspring!
A beautiful example of co-display. Here, the female holds her wings open, a sign that she is ready to mate.
This little guy was successful!
Life after lekking
After mating, the female lays her eggs. After about 26 days, the four eggs hatch. The chicks are given a metal ring, while the mothers receive an orange ring with a two-letter code. They are also fitted with a radio tag, allowing us to track them with our giant antenna in the field. By analyzing the movements picked up by the antenna, Jelena (the doctoral researcher for this project) can determine whether the bird family is still alive. By early July, most nests have hatched, leaving only one task: the female raising the chicks.
Males initially try to mate as much as possible. Once the peak of the lek season is over, and most females already have a nest, they become more opportunistic. From June onwards, you can often see several males chasing females and harassing them. This can sometimes be successful, especially when the female has lost her first clutch due to unforeseen circumstances. From July onwards, the males already migrate south. The period after mating still holds many uncertainties; for example, it's very likely that some males fly further to display again. GPS transmitters will eventually be able to answer this question!
A ringed and tagged male on the lookout later in the season.
A freshly hatched chick.
An older ringed chick exploring the grassland further after release (under the watchful eye of the mother)
Ruffs are fascinating birds that can serve as an indicator or flagship species for coastal grasslands. In the future, we hope to conduct further research into effective management practices that benefit the endangered wading birds that inhabit these habitats. For example, artificial mounds were created in 2021, which will hopefully serve as leks in the future. If this proves successful, it has the potential to become an important management method.
To be continued!
A very big thank you to Jelena Belojević, Veronika Rohr-Bender, Kari Koivula, Lisa Kreye , Jacopo Saccinto, Francesco Rossi, Vell-Matti Pakanen, Kriszti Kupán, Clemens Küpper, and all the other people involved!
More information:
- About Ruff ecology in general: Baguette M. et al. 2022 - Evolutionary Ecology of Fixed Alternative Male Mating Strategies in the Ruff (Calidris pugnax)
- About the genetics behind the different morphs: Clemens K. et al 2016 - A supergene determines highly divergent male reproductive morphs in the ruff
- About some of genetics and hormonal proccesses causing the alternative mating strategies: Giraldo-Deck L. M. et al. 2024 A supergene affects androgen concentrations during early development in a bird with alternative reproductive morphs