If you’re not strong, you must be smart.
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 into extinction, mostly related to the intensification of agricultural practices. In Scandinavia and Eastern Europe, the ruff is still common. In Scandinavia, you have populations in the tundra in the north and coastal meadows or agricultural fields in the south. Around Oulu, researchers have been investigating ruff behaviour for the past eight years. Although my previous blog was about dunlins, the lion's share of my time was spent on ruffs.
Beloved ruff habitat!
Ruffs return to coastal grasslands in early May when the snow finally melts and the ground is no longer frozen. For researchers, this is immediately a hectic period. Ruff males flock together on mounds in the landscape, which are called lekking sites. On these "stages", the males give their best effort to attract females. This behaviour in itself is special as lekking behaviour is rare. Another species also known for this behavioural is the black grouse. However, the ruff adds another level to it.
Ruffs exhibit alternative reproductive tactics. There are different types of males and females! Among males, there is not only a genetic difference but also a clear morphological and behavioural difference. First, there are the dominant males or residents. They are the most aggressive and often have a fixed place on the lek. Secondly, there are the satellite males, who can be recognised by the white ruff. Satellite males are less aggressive and try to gain access to females by cooperating (=co-displaying) with a dominant male. When this dominant male is not paying attention, the satellite male can profit from the situation to do his thing: pass on genes to the next generation. In addition, and very rarely, you have the feader males. These are males that look like females. By doing so, they try to fool the dominant and satellite males to gain access to a female without too much of a fight.
From left to right: one satellite male, three dominant males and a female on the far right.
So, what happened? The explanation behind this remarkable phenomenon lies mainly in genetics. 3.8 million years ago, an inversion within the gene responsible for the birds' hormone balance created two male types: the dominants and the feaders. Later, About 70 000 years ago, a recombination within that supergene gave rise to the satellite males. Fascinating right? I won’t delve into the entire hormone story, as it is complex, and much remains unclear. If you are interested, this paper sheds some light on this. One last fun fact to conclude is that the sneaky feather males have the most sperm. The chances of mating are limited, but when they get a chance, they do it well! So, if you are not the strongest, you just need to be a bit smarter than the others...
Below some pictures of the fieldwork, additional information can be found when clicking on the picture.
Mist nets at the lekking site to capture males.
A male receives a radio tags
This giant antenna receives the signal of all the radio tags. Each field day we can download the data.
Let's spy!
Much of my fieldwork in May involved observing courtship dysplays. This involved counting the males present, the different morphs present, noting whether females visited the lek, and possible copulations. We also attempted to capture birds to ring them and to attach a radio tag. The latter provides valuable information about the birds' landscape use. The following videos will give you an idea about the behavior of these rascals. Each day started at three in the morning. After two cups of coffee and a banana, we drove to the meadow. By five or six o'clock, we were back in the car. The rest of the morning then consisted of catching up on sleep. Often in the evening, we would go back to the field site. One thing is for sure: you can't speak of a natural rhythm here. But I am not complaining. This is nature experience and ornithology par excellence!
I had the luck - and duty - to film during the behavioral observations. In the first video, you see male ruffs jump to attract females. They do this often when a female flies close to the lek site. Indeed, at the end of the video, you can see a female land. In this video you can see five dominant males and one satellite male (note the white ruff and tuft). The individual with the white ruff and black tuft is a dominant male nicknamed Maestro as he is both striking and rather successful.
Once a female lands on the lek, a lot can happen. Dominant males can start to fight, or satellite males can try to cooperate with a dominant male, which is called codisplaying. In the next video, you can see the chaos on the lek. Several males are involved in a fight, and two satellite males try to impress the female. In the 20th second, you can see both satellite males codisplaying with a dominant male. This may have benefits for both males. The interplay between the two males may attract a female so the dominant male can mate, or the satellite male can profit from being close to the female when his dominant male is involved in a fight and ignores the female. To show his dominance towards the satellite male, dominant males put their bill on top of the head of satellite males (somewhat resembling the act of knighting in medieval times).
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....
After the female copulates, she needs to lay eggs. About 26 days later, the four eggs will hatch. The chicks will receive a metal ring, while the mothers will get an orange ring with a two-letter code. They will also be fitted with a radio tag, allowing us to track them using our giant antenna in the field. By analyzing the movements collected by the antenna, which are visible on a computer screen, Jelena - the PhD student working on ruffs and dunlins in Oulu - can determine whether the brood is still alive. In early July, most nests have hatched, leaving only one task: chick-rearing by the female. By then, most males have already departed for their wintering grounds in the Sahel and to a lesser extent coastal regions in Western-Europe.
This video shows the movement of a ruff family over 21 days. Each color represents three days. Note how the family slowly but steadily expands their activity range. Close to the water (upper side), there was a colony of arctic terns and little gulls. This colony seemed to work well as a predator alarm system.
As mentioned in the previous blog, several factors threaten waders in the coastal meadows. Most nests/chicks die due to predation, e.g. by foxes or harriers. Increased flooding risk puts additional pressure on the population. Contrary to Belgium or the Netherlands, ruffs are (still) common breeding birds in Finland (about 25% of the European population nesting here). It will be interesting to see if the northern populations follow in the footsteps of their southern counterparts... For now, ruffs still have plenty of breeding habitat left in Finland. Changes in land use, climate change, and other anthropogenic factors put the populations at risk.
These past two months have once again opened my eyes to the importance of scientific research in understanding the fascinating diversity of animals and behaviors around us. Let’s hope that future generations will still be able to enjoy the astonishing and captivating behaviour of ruffs. To turn the tide in the current biodiversity crisis, a system change is needed. This will not be easy, but let’s be the change!
A very big thank you to Jelena Belojević, Kari Koivula, Lisa Kreye , Francesco Rossi, Vell-Matti Pakanen, Kristzina 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